This section describes the NFS tunable parameters.Tuning the NFS Environment NFS Module Parameters nfssrv Module Parameters rpcmod Module Parameters Tunable Parameter For Information Solaris kernel tunables Chapter 2, Solaris Kernel Tunable Parameters Internet Protocol Suite tunable parameters Chapter 4, Internet Protocol Suite Tunable Parameters Network Cache and Accelerator (NCA) tunable parameters Chapter 5, Network Cache and Accelerator Tunable Parameters You can define NFS parameters in the /etc/system file, which is read during the boot process. Each parameter includes the name of its associated kernel module. For more information, see Tuning a Solaris System.The names of the parameters, the modules that they reside in, and the default values can change between releases. Check the documentation for the version of the active SunOS release before making changes or applying values from previous releases. This section describes parameters related to the NFS kernel module.DescriptionControls the caching of pathconf information for NFS Version 3 mounted file systems. Data TypeInteger (32-bit) Default0 (caching enabled) Range0 (caching enabled) or 1 (caching disabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeThe pathconf information is cached on a per file basis. However, if the server can change the information for a specific file dynamically, use this parameter to disable caching. There is no mechanism for the client to validate its cache entry. Commitment LevelUnstable DescriptionControls the caching of pathconf information for NFS Version 4 mounted file systems. Data TypeInteger (32-bit) Default0 (caching enabled) Range0 (caching enabled) or 1 (caching disabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeThe pathconf information is cached on a per file basis. However, if the server can change the information for a specific file dynamically, use this parameter to disable caching. There is no mechanism for the client to validate its cache entry. Commitment LevelUnstable DescriptionControls whether files with incorrect or negative time stamps should be made visible on the client.Historically, neither the NFS client nor the NFS server would do any range checking on the file times being returned. The over-the-wire timestamp values are unsigned and 32-bits long. So, all values have been legal.However, on a system running a 32-bit Solaris kernel, the timestamp values are signed and 32-bits long. Thus, it would be possible to have a timestamp representation that appeared to be prior to January 1, 1970, or pre-epoch.The problem on a system running a 64-bit Solaris kernel is slightly different. The timestamp values on the 64-bit Solaris kernel are signed and 64-bits long. It is impossible to determine whether a time field represents a full 32-bit time or a negative time, that is, a time prior to January 1, 1970.It is impossible to determine whether to sign extend a time value when converting from 32 bits to 64 bits. The time value should be sign extended if the time value is truly a negative number. However, the time value should not be sign extended if it does truly represent a full 32-bit time value. This problem is resolved by simply disallowing full 32-bit time values. Data TypeInteger (32-bit) Default0 (32-bit time stamps disabled) Range0 (32-bit time stamps disabled) or 1 (32-bit time stamps enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeEven during normal operation, it is possible for the timestamp values on some files to be set very far in the future or very far in the past. If access to these files is preferred using NFS mounted file systems, set this parameter to 1 to allow the timestamp values to be passed through unchecked. Commitment LevelUnstable DescriptionControls the default RPC timeout for NFS version 2 mounted file systems using connection-oriented transports such as TCP for the transport protocol. Data TypeSigned integer (32-bit) Default600 (60 seconds) Range0 to 231 - 1 Units10th of seconds Dynamic?Yes, but the RPC timeout for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTCP does a good job ensuring requests and responses are delivered appropriately. However, if the round-trip times are very large in a particularly slow network, the NFS version 2 client might time out prematurely.Increase this parameter to prevent the client from timing out incorrectly. The range of values is very large, so increasing this value too much might result in situations where a retransmission is not detected for long periods of time. Commitment LevelUnstable DescriptionControls the default RPC timeout for NFS version 3 mounted file systems using connection-oriented transports such as TCP for the transport protocol. Data TypeSigned integer (32-bit) Default600 (60 seconds) Range0 to 231 - 1 Units10th of seconds Dynamic?Yes, but the RPC timeout for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTCP does a good job ensuring requests and responses are delivered appropriately. However, if the round-trip times are very large in a particularly slow network, the NFS version 3 client might time out prematurely.Increase this parameter to prevent the client from timing out incorrectly. The range of values is very large, so increasing this value too much might result in situations where a retransmission is not detected for long periods of time. Commitment LevelUnstable DescriptionControls the default RPC timeout for NFS version 4 mounted file systems using connection-oriented transports such as TCP for the transport protocol. The NFS Version 4 protocol specification disallows retransmission over the same TCP connection. Thus, this parameter primarily controls how quickly the client responds to certain events, such as detecting a forced unmount operation or detecting how quickly the server fails over to a new server. Data TypeSigned integer (32-bit) Default600 (60 seconds) Range0 to 231 - 1 Units10th of seconds Dynamic?Yes, but this parameter is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTCP does a good job ensuring requests and responses are delivered appropriately. However, if the round-trip times are very large in a particularly slow network, the NFS version 4 client might time out prematurely.Increase this parameter to prevent the client from timing out incorrectly. The range of values is very large, so increasing this value too much might result in situations where a retransmission is not detected for long periods of time. Commitment LevelUnstable DescriptionControls whether the contents of symbolic link files are cached for NFS version 2 mounted file systems. Data TypeInteger (32–bit) Default1 (caching enabled) Range0 (caching disabled) or 1 (caching enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeIf a server changes the contents of a symbolic link file without updating the modification timestamp on the file or if the granularity of the timestamp is too large, then changes to the contents of the symbolic link file might not be visible on the client for extended periods. In this case, use this parameter to disable the caching of symbolic link contents. Doing so makes the changes immediately visible to applications running on the client. Commitment LevelUnstable DescriptionControls whether the contents of symbolic link files are cached for NFS version 3 mounted file systems. Data TypeInteger (32-bit) Default1 (caching enabled) Range0 (caching disabled) or 1 (caching enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeIf a server changes the contents of a symbolic link file without updating the modification timestamp on the file or if the granularity of the timestamp is too large, then changes to the contents of the symbolic link file might not be visible on the client for extended periods. In this case, use this parameter to disable the caching of symbolic link contents. Doing so makes the changes immediately visible to applications running on the client. Commitment LevelUnstable DescriptionControls whether the contents of symbolic link files are cached for NFS version 4 mounted file systems. Data TypeInteger (32-bit) Default1 (caching enabled) Range0 (caching disabled) or 1 (caching enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeIf a server changes the contents of a symbolic link file without updating the modification timestamp on the file or if the granularity of the timestamp is too large, then changes to the contents of the symbolic link file might not be visible on the client for extended periods. In this case, use this parameter to disable the caching of symbolic link contents. Doing so makes the changes immediately visible to applications running on the client. Commitment LevelUnstable DescriptionControls whether a feature known as dynamic retransmission is enabled for NFS version 2 mounted file systems using connectionless transports such as UDP. This feature attempts to reduce retransmissions by monitoring server response times and then adjusting RPC timeouts and read- and write- transfer sizes. Data TypeInteger (32-bit) Default1 (enabled) Range0 (disabled) or 1 (enabled) Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeDo not change this parameter. Commitment LevelUnstable DescriptionControls whether a feature known as dynamic retransmission is enabled for NFS version 3 mounted file systems using connectionless transports such as UDP. This feature attempts to reduce retransmissions by monitoring server response times and then adjusting RPC timeouts and read- and write- transfer sizes. Data TypeInteger (32-bit) Default0 (disabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeDo not change this parameter. Commitment LevelUnstable DescriptionControls whether a negative name cache is used for NFS version 2 mounted file systems. This negative name cache records file names that were looked up, but not found. The cache is used to avoid over-the-network look-up requests made for file names that are already known to not exist. Data TypeInteger (32-bit) Default1 (enabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeFor the cache to perform correctly, negative entries must be strictly verified before they are used. This consistency mechanism is relaxed slightly for read-only mounted file systems. It is assumed that the file system on the server is not changing or is changing very slowly, and that it is okay for such changes to propagate slowly to the client. The consistency mechanism becomes the normal attribute cache mechanism in this case.If file systems are mounted read-only on the client, but are expected to change on the server and these changes need to be seen immediately by the client, use this parameter to disable the negative cache.If you disable the nfs:nfs_disable_rddir_cache parameter, you should probably also disable this parameter. For more information, see nfs:nfs_disable_rddir_cache. Commitment LevelUnstable DescriptionControls whether a negative name cache is used for NFS version 3 mounted file systems. This negative name cache records file names that were looked up, but were not found. The cache is used to avoid over-the-network look-up requests made for file names that are already known to not exist. Data TypeInteger (32-bit) Default1 (enabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeFor the cache to perform correctly, negative entries must be strictly verified before they are used. This consistency mechanism is relaxed slightly for read-only mounted file systems. It is assumed that the file system on the server is not changing or is changing very slowly, and that it is okay for such changes to propagate slowly to the client. The consistency mechanism becomes the normal attribute cache mechanism in this case. If file systems are mounted read-only on the client, but are expected to change on the server and these changes need to be seen immediately by the client, use this parameter to disable the negative cache.If you disable the nfs:nfs_disable_rddir_cache parameter, you should probably also disable this parameter. For more information, see nfs:nfs_disable_rddir_cache. Commitment LevelUnstable DescriptionControls whether a negative name cache is used for NFS version 4 mounted file systems. This negative name cache records file names that were looked up, but were not found. The cache is used to avoid over-the-network look-up requests made for file names that are already known to not exist. Data TypeInteger (32-bit) Default1 (enabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeFor the cache to perform correctly, negative entries must be strictly verified before they are used. This consistency mechanism is relaxed slightly for read-only mounted file systems. It is assumed that the file system on the server is not changing or is changing very slowly, and that it is okay for such changes to propagate slowly to the client. The consistency mechanism becomes the normal attribute cache mechanism in this case. If file systems are mounted read-only on the client, but are expected to change on the server and these changes need to be seen immediately by the client, use this parameter to disable the negative cache.If you disable the nfs:nfs_disable_rddir_cache parameter, you should probably also disable this parameter. For more information, see nfs:nfs_disable_rddir_cache. Commitment LevelUnstable DescriptionControls the number of kernel threads that perform asynchronous I/O for the NFS version 2 client. Because NFS is based on RPC and RPC is inherently synchronous, separate execution contexts are required to perform NFS operations that are asynchronous from the calling thread.The operations that can be executed asynchronously are read for read-ahead, readdir for readdir read-ahead, write for putpage and pageio operations, commit, and inactive for cleanup operations that the client performs when it stops using a file. Data TypeInteger (16-bit) Default8 Range0 to 215 - 1 UnitsThreads Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTo increase or reduce the number of simultaneous I/O operations that are outstanding at any given time. For example, for a very low bandwidth network, you might want to decrease this value so that the NFS client does not overload the network. Alternately, if the network is very high bandwidth, and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable DescriptionControls the number of kernel threads that perform asynchronous I/O for the NFS version 3 client. Because NFS is based on RPC and RPC is inherently synchronous, separate execution contexts are required to perform NFS operations that are asynchronous from the calling thread.The operations that can be executed asynchronously are read for read-ahead, readdir for readdir read-ahead, write for putpage and pageio requests, and commit. Data TypeInteger (16-bit) Default8 Range0 to 215 - 1 UnitsThreads Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTo increase or reduce the number of simultaneous I/O operations that are outstanding at any given time. For example, for a very low bandwidth network, you might want to decrease this value so that the NFS client does not overload the network. Alternately, if the network is very high bandwidth, and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable DescriptionControls the number of kernel threads that perform asynchronous I/O for the NFS version 4 client. Because NFS is based on RPC and RPC is inherently synchronous, separate execution contexts are required to perform NFS operations that are asynchronous from the calling thread.The operations that can be executed asynchronously are read for read-ahead, write-behind, directory read-ahead, and cleanup operations that the client performs when it stops using a file. Data TypeInteger (16-bit) Default8 Range0 to 215 - 1 UnitsThreads Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone When to ChangeTo increase or reduce the number of simultaneous I/O operations that are outstanding at any given time. For example, for a very low bandwidth network, you might want to decrease this value so that the NFS client does not overload the network. Alternately, if the network is very high bandwidth, and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable DescriptionControls the number of read-ahead operations that are queued by the NFS version 2 client when sequential access to a file is discovered. These read-ahead operations increase concurrency and read throughput. Each read-ahead request is generally for one logical block of file data. Data TypeInteger (32-bit) Default4 Range0 to 231 - 1 UnitsLogical blocks. (See nfs:nfs_bsize.) Dynamic?Yes ValidationNone When to ChangeTo increase or reduce the number of read-ahead requests that are outstanding for a specific file at any given time. For example, for a very low bandwidth network or on a low memory client, you might want to decrease this value so that the NFS client does not overload the network or the system memory. Alternately, if the network is very high bandwidth, and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable DescriptionControls the number of read-ahead operations that are queued by the NFS version 3 client when sequential access to a file is discovered. These read-ahead operations increase concurrency and read throughput. Each read-ahead request is generally for one logical block of file data. Data TypeInteger (32-bit) Default4 Range0 to 231 - 1 UnitsLogical blocks. (See nfs:nfs3_bsize.) Dynamic?Yes ValidationNone When to ChangeTo increase or reduce the number of read-ahead requests that are outstanding for a specific file at any given time. For example, for a very low bandwidth network or on a low memory client, you might want to decrease this value so that the NFS client does not overload the network or the system memory. Alternately, if the network is very high bandwidth and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable Change HistoryFor information, see nfs:nfs3_nra (Solaris 10). DescriptionControls the number of read-ahead operations that are queued by the NFS version 4 client when sequential access to a file is discovered. These read-ahead operations increase concurrency and read throughput. Each read-ahead request is generally for one logical block of file data. Data TypeInteger (32-bit) Default4 Range0 to 231 - 1 UnitsLogical blocks. (See nfs:nfs4_bsize.) Dynamic?Yes ValidationNone When to ChangeTo increase or reduce the number of read-ahead requests that are outstanding for a specific file at any given time. For example, for a very low bandwidth network or on a low memory client, you might want to decrease this value so that the NFS client does not overload the network or the system memory. Alternately, if the network is very high bandwidth, and the client and server have sufficient resources, you might want to increase this value. Doing so can more effectively utilize the available network bandwidth, and the client and server resources. Commitment LevelUnstable DescriptionControls the size of the rnode cache on the NFS client.The rnode, used by both NFS version 2, 3, and 4 clients, is the central data structure that describes a file on the NFS client. The rnode contains the file handle that identifies the file on the server. The rnode also contains pointers to various caches used by the NFS client to avoid network calls to the server. Each rnode has a one-to-one association with a vnode. The vnode caches file data.The NFS client attempts to maintain a minimum number of rnodes to attempt to avoid destroying cached data and metadata. When an rnode is reused or freed, the cached data and metadata must be destroyed. Data TypeInteger (32-bit) DefaultThe default setting of this parameter is 0, which means that the value of nrnode should be set to the value of the ncsize parameter. Actually, any non positive value of nrnode results in nrnode being set to the value of ncsize. Range1 to 231 - 1 Unitsrnodes Dynamic?No. This value can only be changed by adding or changing the parameter in the /etc/system file, and then rebooting the system. ValidationThe system enforces a maximum value such that the rnode cache can only consume 25 percent of available memory. When to ChangeBecause rnodes are created and destroyed dynamically, the system tends to settle upon a nrnode-size cache, automatically adjusting the size of the cache as memory pressure on the system increases or as more files are simultaneously accessed. However, in certain situations, you could set the value of nrnode if the mix of files being accessed can be predicted in advance. For example, if the NFS client is accessing a few very large files, you could set the value of nrnode to a small number so that system memory can cache file data instead of rnodes. Alternately, if the client is accessing many small files, you could increase the value of nrnode to optimize for storing file metadata to reduce the number of network calls for metadata.Although it is not recommended, the rnode cache can be effectively disabled by setting the value of nrnode to 1. This value instructs the client to only cache 1 rnode, which means that it is reused frequently. Commitment LevelUnstable Change HistoryFor information, see nfs:nrnode (Solaris 9 8/03). DescriptionSome older NFS servers might incorrectly handle NFS version 2 READDIR requests for more than 1024 bytes of directory information. This problem is due to a bug in the server implementation. However, this parameter contains a workaround in the NFS version 2 client.When this parameter is enabled, the client does not generate a READDIR request for larger than 1024 bytes of directory information. If this parameter is disabled, then the over-the-wire size is set to the lesser of either the size passed in by using the getdents system call or by using NFS_MAXDATA, which is 8192 bytes. For more information, see getdents2. Data TypeInteger (32-bit) Default0 (disabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter if an older NFS version 2 only server is used and interoperability problems occur when the server tries to read directories. Enabling this parameter might cause a slight decrease in performance for applications that read directories. Commitment LevelUnstable DescriptionSome older NFS servers might incorrectly handle NFS version 3 READDIR requests for more than 1024 bytes of directory information. This problem is due to a bug in the server implementation. However, this parameter contains a workaround in the NFS version 3 client.When this parameter is enabled, the client does not generate a READDIR request for larger than 1024 bytes of directory information. If this parameter is disabled, then the over-the-wire size is set to the minimum of either the size passed in by using the getdents system call or by using MAXBSIZE, which is 8192 bytes. For more information, see getdents2. Data TypeInteger (32-bit) Default0 (disabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter if an older NFS version 3 only server is used and interoperability problems occur when the server tries to read directories. Enabling this parameter might cause a slight decrease in performance for applications that read directories. Commitment LevelUnstable DescriptionSome NFS servers might incorrectly handle NFS version 4 READDIR requests for more than 1024 bytes of directory information. This problem is due to a bug in the server implementation. However, this parameter contains a workaround in the NFS version 4 client.When this parameter is enabled, the client does not generate a READDIR request for larger than 1024 bytes of directory information. If this parameter is disabled, then the over-the-wire size is set to the lesser of either the size passed in by using the getdents system call or by using MAXBSIZE, which is 8192 bytes. For more information, see getdents2. Data TypeInteger (32-bit) Default0 (disabled) Range0 (disabled) or 1 (enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter if an NFS version 4 only server is used and interoperability problems occur when the server tries to read directories. Enabling this parameter might cause a slight performance drop for applications that read directories. Commitment LevelUnstable DescriptionControls the time duration in between logging ENOSPC and EDQUOT write errors received by the NFS client. This parameter affects NFS version 2, 3, and 4 clients. Data TypeLong integer (32 bits on 32-bit platforms and 64 bits on 64-bit platforms) Default5 seconds Range0 to 231 - 1 on 32-bit platforms0 to 263 - 1 on 64-bit platforms UnitsSeconds Dynamic?Yes ValidationNone When to ChangeIncrease or decrease the value of this parameter in response to the volume of messages being logged by the client. Typically, you might want to increase the value of this parameter to decrease the number of out of space messages being printed when a full file system on a server is being actively used. Commitment LevelUnstable Change HistoryFor information, see nfs:nfs_write_error_interval (Solaris 9 8/03). DescriptionControls whether NFS write errors are logged to the system console and syslog or to the system console only. This parameter affects messages for NFS version 2, 3, and 4 clients. Data TypeInteger (32-bit) Default0 (system console and syslog) Range0 (system console and syslog) or 1 (system console) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter to avoid filling up the file system containing the messages logged by the syslogd daemon. When this parameter is enabled, messages are printed on the system console only and are not copied to the syslog messages file. Commitment LevelUnstable Change HistoryFor information, see nfs:nfs_write_error_to_cons_only (Solaris 9 8/03). DescriptionControls the use of a cache to hold responses from READDIR and READDIRPLUS requests. This cache avoids over-the-wire calls to the server to retrieve directory information. Data TypeInteger (32-bit) Default0 (caching enabled) Range0 (caching enabled) or 1 (caching disabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter if interoperability problems develop due to a server that does not update the modification time on a directory when a file or directory is created in it or removed from it. The symptoms are that new names do not appear in directory listings after they have been added to the directory or that old names do not disappear after they have been removed from the directory.This parameter controls the caching for NFS version 2, 3, and 4 mounted file systems. This parameter applies to all NFS mounted file systems, so caching cannot be disabled or enabled on a per file system basis.If you disable this parameter, you should also disable the following parameters to to prevent bad entries in the DNLC negative cache:nfs:nfs_lookup_neg_cache nfs:nfs3_lookup_neg_cache nfs:nfs4_lookup_neg_cache Commitment LevelUnstable Change HistoryFor information, see nfs:nfs_disable_rddir_cache (Solaris 9 8/03). DescriptionControls the logical block size used by the NFS version 2 client. This block size represents the amount of data that the client attempts to read from or write to the server when it needs to do an I/O. Data TypeUnsigned integer (32-bit) Default8192 bytes Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but the block size for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. Setting this parameter too low or too high might cause the system to malfunction. Do not set this parameter to anything less than PAGESIZE for the specific platform. Do not set this parameter too high because it might cause the system to hang while waiting for memory allocations to be granted. When to ChangeDo not change this parameter. Commitment LevelUnstable DescriptionControls the logical block size used by the NFS version 3 client. This block size represents the amount of data that the client attempts to read from or write to the server when it needs to do an I/O. Data TypeUnsigned integer (32-bit) Default32,768 (32 Kbytes) Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but the block size for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. Setting this parameter too low or too high might cause the system to malfunction. Do not set this parameter to anything less than PAGESIZE for the specific platform. Do not set this parameter too high because it might cause the system to hang while waiting for memory allocations to be granted. When to ChangeExamine the value of this parameter when attempting to change the maximum data transfer size. Change this parameter in conjunction with the nfs:nfs3_max_transfer_size parameter. If larger transfers are preferred, increase both parameters. If smaller transfers are preferred, then just reducing this parameter should suffice. Commitment LevelUnstable DescriptionControls the logical block size used by the NFS version 4 client. This block size represents the amount of data that the client attempts to read from or write to the server when it needs to do an I/O. Data TypeUnsigned integer (32-bit) Default32,768 (32 Kbytes) Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but the block size for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. Setting this parameter too low or too high might cause the system to malfunction. Do not set this parameter to anything less than PAGESIZE for the specific platform. Do not set this parameter too high because it might cause the system to hang while waiting for memory allocations to be granted. When to ChangeExamine the value of this parameter when attempting to change the maximum data transfer size. Change this parameter in conjunction with the nfs:nfs4_max_transfer_size parameter. If larger transfers are preferred, increase both parameters. If smaller transfers are preferred, then just reducing this parameter should suffice. Commitment LevelUnstable DescriptionControls the mix of asynchronous requests that are generated by the NFS version 2 client. The four types of asynchronous requests are read-ahead, putpage, pageio, and readdir-ahead. The client attempts to round-robin between these different request types to attempt to be fair and not starve one request type in favor of another.However, the functionality in some NFS version 2 servers such as write gathering depends upon certain behaviors of existing NFS Version 2 clients. In particular, this functionality depends upon the client sending out multiple WRITE requests at about the same time. If one request is taken out of the queue at a time, the client would be defeating this server functionality designed to enhance performance for the client.Thus, use this parameter to control the number of requests of each request type that are sent out before changing types. Data TypeUnsigned integer (32-bit) Default1 Range0 to 231 - 1 UnitsAsynchronous requests Dynamic?Yes, but the cluster setting for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the value of this parameter to 0 causes all of the queued requests of a particular request type to be processed before moving on to the next type. This effectively disables the fairness portion of the algorithm. When to ChangeTo increase the number of each type of asynchronous request that is generated before switching to the next type. Doing so might help with server functionality that depends upon clusters of requests coming from the client. Commitment LevelUnstable DescriptionControls the mix of asynchronous requests that are generated by the NFS version 3 client. The five types of asynchronous requests are read-ahead, putpage, pageio, readdir-ahead, and commit. The client attempts to round-robin between these different request types to attempt to be fair and not starve one request type in favor of another.However, the functionality in some NFS version 3 servers such as write gathering depends upon certain behaviors of existing NFS version 3 clients. In particular, this functionality depends upon the client sending out multiple WRITE requests at about the same time. If one request is taken out of the queue at a time, the client would be defeating this server functionality designed to enhance performance for the client.Thus, use this parameter to control the number of requests of each request type that are sent out before changing types. Data TypeUnsigned integer (32-bit) Default1 Range0 to 231 - 1 UnitsAsynchronous requests Dynamic?Yes, but the cluster setting for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the value of this parameter to 0 causes all of the queued requests of a particular request type to be processed before moving on to the next type. This value effectively disables the fairness portion of the algorithm. When to ChangeTo increase the number of each type of asynchronous operation that is generated before switching to the next type. Doing so might help with server functionality that depends upon clusters of operations coming from the client. Commitment LevelUnstable DescriptionControls the mix of asynchronous requests that are generated by the NFS version 4 client. The six types of asynchronous requests are read-ahead, putpage, pageio, readdir-ahead, commit, and inactive. The client attempts to round-robin between these different request types to attempt to be fair and not starve one request type in favor of another.However, the functionality in some NFS version 4 servers such as write gathering depends upon certain behaviors of existing NFS version 4 clients. In particular, this functionality depends upon the client sending out multiple WRITE requests at about the same time. If one request is taken out of the queue at a time, the client would be defeating this server functionality designed to enhance performance for the client.Thus, use this parameter to control the number of requests of each request type that are sent out before changing types. Data TypeUnsigned integer (32-bit) Default1 Range0 to 231 - 1 UnitsAsynchronous requests Dynamic?Yes, but the cluster setting for a file system is set when the file system is mounted. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the value of this parameter to 0 causes all of the queued requests of a particular request type to be processed before moving on to the next type. This effectively disables the fairness portion of the algorithm. When to ChangeTo increase the number of each type of asynchronous request that is generated before switching to the next type. Doing so might help with server functionality that depends upon clusters of requests coming from the client. Commitment LevelUnstable DescriptionControls the duration of time that threads, which execute asynchronous I/O requests, sleep with nothing to do before exiting. When there are no more requests to execute, each thread goes to sleep. If no new requests come in before this timer expires, the thread wakes up and exits. If a request does arrive, a thread is woken up to execute requests until there are none again. Then, the thread goes back to sleep waiting for another request to arrive, or for the timer to expire. Data TypeInteger (32-bit) Default6000 (1 minute expressed as 60 sec * 100Hz) Range0 to 231 - 1 UnitsHz. (Typically, the clock runs at 100Hz.) Dynamic?Yes ValidationNone. However, setting this parameter to a non positive value causes these threads exit as soon as there are no requests in the queue for them to process. When to ChangeIf the behavior of applications in the system is known precisely and the rate of asynchronous I/O requests can be predicted, it might be possible to tune this parameter to optimize performance slightly in either of the following ways:By making the threads expire more quickly, thus freeing up kernel resources more quickly By making the threads expire more slowly, thus avoiding thread create and destroy overhead Commitment LevelUnstable DescriptionTunes the number of hash queues that access the file access cache on the NFS client. The file access cache stores file access rights that users have with respect to files that they are trying to access. The cache itself is dynamically allocated. However, the hash queues used to index into the cache are statically allocated. The algorithm assumes that there is one access cache entry per active file and four of these access cache entries per hash bucket. Thus, by default, the value of this parameter is set to the value of the nrnode parameter. Data TypeInteger (32-bit) DefaultThe default setting of this parameter is 0. This value means that the value of nacache should be set to the value of the nrnode parameter. Range1 to 231 - 1 UnitsAccess cache entries Dynamic?No. This value can only be changed by adding or changing the parameter in the /etc/system file, and then rebooting system. ValidationNone. However, setting this parameter to a negative value will probably cause the system to try to allocate a very large set of hash queues. While trying to do so, the system is likely to hang. When to ChangeExamine the value of this parameter if the basic assumption of one access cache entry per file would be violated. This violation could occur for systems in a timesharing mode where multiple users are accessing the same file at about the same time. In this case, it might be helpful to increase the expected size of the access cache so that the hashed access to the cache stays efficient. Commitment LevelUnstable DescriptionControls the duration of time that the NFS version 3 client waits to transmit a new request after receiving the NFS3ERR_JUKEBOX error from a previous request. The NFS3ERR_JUKEBOX error is generally returned from the server when the file is temporarily unavailable for some reason. This error is generally associated with hierarchical storage, and CD or tape jukeboxes. Data TypeLong integer (32 bits on 32-bit platforms and 64 bits on 64-bit platforms) Default1000 (10 seconds expressed as 10 sec * 100Hz) Range0 to 231 - 1 on 32-bit platforms0 to 263 - 1 on 64-bit platforms UnitsHz. (Typically, the clock runs at 100Hz.) Dynamic?Yes ValidationNone When to ChangeExamine the value of this parameter and perhaps adjust it to match the behaviors exhibited by the server. Increase this value if the delays in making the file available are long in order to reduce network overhead due to repeated retransmissions. Decrease this value to reduce the delay in discovering that the file has become available. Commitment LevelUnstable DescriptionControls the maximum size of the data portion of an NFS version 3 READ, WRITE, READDIR, or READDIRPLUS request. This parameter controls both the maximum size of the request that the server returns as well as the maximum size of the request that the client generates. Data TypeInteger (32-bit) Default1,048,576 (1 Mbyte) Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the maximum transfer size on the server to 0 is likely to cause clients to malfunction or just decide not to attempt to talk to the server.There is also a limit on the maximum transfer size when using NFS over the UDP transport. UDP has a hard limit of 64 Kbytes per datagram. This 64 Kbytes must include the RPC header as well as other NFS information, in addition to the data portion of the request. Setting the limit too high might result in errors from UDP and communication problems between the client and the server. When to ChangeTo tune the size of data transmitted over the network. In general, the nfs:nfs3_bsize parameter should also be updated to reflect changes in this parameter. For example, when you attempt to increase the transfer size beyond 32 Kbytes, update nfs:nfs3_bsize to reflect the increased value. Otherwise, no change in the over-the-wire request size is observed. For more information, see nfs:nfs3_bsize.If you want to use a smaller transfer size than the default transfer size, use the mount command's wsize or rsize option on a per-file system basis. Commitment LevelUnstable Change HistoryFor information, see nfs:nfs3_max_transfer_size (Solaris 9 8/03). DescriptionControls the maximum size of the data portion of an NFS version 4 READ, WRITE, READDIR, or READDIRPLUS request. This parameter controls both the maximum size of the request that the server returns as well as the maximum size of the request that the client generates. Data TypeInteger (32-bit) Default32, 768 (32 Kbytes) Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the maximum transfer size on the server to 0 is likely to cause clients to malfunction or just decide not to attempt to talk to the server.There is also a limit on the maximum transfer size when using NFS over the UDP transport. For more information on the maximum for UDP, see nfs:nfs3_max_transfer_size. When to ChangeTo tune the size of data transmitted over the network. In general, the nfs:nfs4_bsize parameter should also be updated to reflect changes in this parameter.For example, when you attempt to increase the transfer size beyond 32 Kbytes, update nfs:nfs4_bsize to reflect the increased value. Otherwise, no change in the over-the-wire request size is observed. For more information, see nfs:nfs4_bsize.If you want to use a smaller transfer size than the default transfer size, use the mount command's wsize or rsize option on a per-file system basis. Commitment LevelUnstable DescriptionControls the maximum size of the data portion of an NFS version 3 READ, WRITE, READDIR, or READDIRPLUS request over UDP. This parameter controls both the maximum size of the request that the server returns as well as the maximum size of the request that the client generates. Data TypeInteger (32-bit) Default32, 768 (32 Kbytes) Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the maximum transfer size on the server to 0 is likely to cause clients to malfunction or just decide not to attempt to talk to the server. When to ChangeDo not change this parameter. Commitment LevelUnstable DescriptionControls the maximum size of the data portion of an NFS version 3 READ, WRITE, READDIR, or READDIRPLUS request over TCP. This parameter controls both the maximum size of the request that the server returns as well as the maximum size of the request that the client generates. Data TypeInteger (32-bit) Default1048576 bytes Range0 to 231 - 1 UnitsBytes Dynamic?Yes, but this parameter is set per file system at mount time. To affect a particular file system, unmount and mount the file system after changing this parameter. ValidationNone. However, setting the maximum transfer size on the server to 0 is likely to cause clients to malfunction or just decide not to attempt to talk to the server. When to ChangeDo not change this parameter unless transfer sizes larger than 1 Mbyte are preferred. Commitment LevelUnstable This section describes NFS parameters for the nfssrv module.DescriptionControls some security checking that the NFS server attempts to do to enforce integrity on the part of its clients. The NFS server can check whether the source port from which a request was sent was a reserved port. A reserved port has a number less than 1024. For BSD-based systems, these ports are reserved for processes being run by root. This security checking can prevent users from writing their own RPC-based applications that defeat the access checking that the NFS client uses. Data TypeInteger (32-bit) Default0 (security checking disabled) Range0 (security checking disabled) or 1 (security checking enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeUse this parameter to prevent malicious users from gaining access to files by using the NFS server that they would not ordinarily have access to. However, the reserved port notion is not universally supported. Thus, the security aspects of the check are very weak. Also, not all NFS client implementations bind their transport endpoints to a port number in the reserved range. Thus, interoperability problems might result if the security checking is enabled. Commitment LevelUnstable DescriptionControls the behavior of the NFS version 2 server when it processes WRITE requests. The NFS version 2 protocol mandates that all modified data and metadata associated with the WRITE request reside on stable storage before the server can respond to the client. NFS version 2 WRITE requests are limited to 8192 bytes of data. Thus, each WRITE request might cause multiple small writes to the storage subsystem. This can cause a performance problem.One method to accelerate NFS version 2 WRITE requests is to take advantage of a client behavior. Clients tend to send WRITE requests in batches. The server can take advantage of this behavior by clustering together the different WRITE requests into a single request to the underlying file system. Thus, the data to be written to the storage subsystem can be written in fewer, larger requests. This method can significantly increase the throughput for WRITE requests. Data TypeInteger (32-bit) Default1 (clustering enabled) Range0 (clustering disabled) or 1 (clustering enabled) UnitsBoolean values Dynamic?Yes ValidationNone When to ChangeSome very small NFS clients, particularly PC clients, might not batch WRITE requests. Thus, the behavior required from the clients might not exist. In addition, the clustering in the NFS version 2 server might just add overhead and slow down performance instead of increasing it. Commitment LevelUnstable DescriptionControls the size of the cache of client handles that contact the NFS authentication server. This server authenticates NFS clients to determine whether they are allowed access to the file handle that they are trying to use. Data TypeInteger (32-bit) Default16 Range0 to 231 - 1 UnitsClient handles Dynamic?Yes ValidationNone When to ChangeThis cache is not dynamic, so attempts to allocate a client handle when all are busy will fail. This failure results in requests being dropped by the NFS server because they could not be authenticated. Most often, this result is not a problem because the NFS client just times out and retransmits the request. However, for soft-mounted file systems on the client, the client might time out, not retry the request, and then return an error to the application. This situation might be avoided if you ensure that the size of the cache on the server is large enough to handle the load. Commitment LevelUnstable DescriptionControls the duration of time that entries are held in the NFS authentication cache before being purged due to memory pressure in the system. Data TypeLong integer (32 bits on 32-bit platforms and 64 bits on 64-bit platforms) Default3600 seconds (1 hour) Range0 to 231 - 1 on 32-bit platforms0 to 263 - 1 on 64-bit platforms UnitsSeconds Dynamic?Yes ValidationNone When to ChangeThe size of the NFS authentication cache can be adjusted by varying the minimum age of entries that can get purged from the cache. The size of the cache should be controlled so that it is not allowed to grow too large, thus using system resources that are not allowed to be released due to this aging process. Commitment LevelUnstable This section describes NFS parameters for the rpcmod module.DescriptionControls the number of TCP connections that the NFS client uses when communicating with each NFS server. The kernel RPC is constructed so that it can multiplex RPCs over a single connection. However, multiple connections can be used, if preferred. Data TypeInteger (32-bit) Default1 Range1 to 231 - 1 UnitsConnections Dynamic?Yes ValidationNone When to ChangeIn general, one connection is sufficient to achieve full network bandwidth. However, if TCP cannot utilize the bandwidth offered by the network in a single stream, then multiple connections might increase the throughput between the client and the server.Increasing the number of connections doesn't come without consequences. Increasing the number of connections also increases kernel resource usage needed to keep track of each connection. Commitment LevelUnstable DescriptionControls the duration of time on the client that a connection between the client and server is allowed to remain idle before being closed. Data TypeLong integer (32 bits on 32-bit platforms and 64 bits on 64-bit platforms) Default300,000 milliseconds (5 minutes) Range0 to 231 - 1 on 32-bit platforms0 to 263 - 1 on 64-bit platforms UnitsMilliseconds Dynamic?Yes ValidationNone When to ChangeUse this parameter to change the time that idle connections are allowed to exist on the client before being closed. You might might want to close connections at a faster rate to avoid consuming system resources. Commitment LevelUnstable DescriptionControls the duration of time on the server that a connection between the client and server is allowed to remain idle before being closed. Data TypeLong integer (32 bits on 32-bit platforms and 64 bits on 64-bit platforms) Default360,000 milliseconds (6 minutes) Range0 to 231 - 1 on 32-bit platforms0 to 263 - 1 on 64-bit platforms UnitsMilliseconds Dynamic?Yes ValidationNone When to ChangeUse this parameter to change the time that idle connections are allowed to exist on the server before being closed. You might want to close connections at a faster rate to avoid consuming system resources. Commitment LevelUnstable DescriptionSets the size of the kernel stack for kernel RPC service threads. Data TypeInteger (32-bit) DefaultThe default value is 0. This value means that the stack size is set to the system default. Range0 to 231 - 1 UnitsBytes Dynamic?Yes, for all new threads that are allocated. The stack size is set when the thread is created. Therefore, changes to this parameter do not affect existing threads but are applied to all new threads that are allocated. ValidationNone When to ChangeVery deep call depths can cause the stack to overflow and cause red zone faults. The combination of a fairly deep call depth for the transport, coupled with a deep call depth for the local file system, can cause NFS service threads to overflow their stacks.Set this parameter to a multiple of the hardware pagesize on the platform. Commitment LevelUnstable DescriptionControls the maximum number of requests that are processed for each transport endpoint before switching transport endpoints. The kernel RPC works by having a pool of service threads and a pool of transport endpoints. Any one of the service threads can process requests from any one of the transport endpoints. For performance, multiple requests on each transport endpoint are consumed before switching to a different transport endpoint. This approach offers performance benefits while avoiding starvation. Data TypeInteger (32-bit) Default8 Range0 to 231 - 1 UnitsRequests Dynamic?Yes, but the maximum number of requests to process before switching transport endpoints is set when the transport endpoint is configured into the kernel RPC subsystem. Changes to this parameter only affect new transport endpoints, not existing transport endpoints. ValidationNone When to ChangeTune this parameter so that services can take advantage of client behaviors such as the clustering that accelerate NFS version 2 WRITE requests. Increasing this parameter might result in the server being better able to take advantage of client behaviors. Commitment LevelUnstable DescriptionControls the size of the duplicate request cache that detects RPC- level retransmissions on connectionless transports. This cache is indexed by the client network address and the RPC procedure number, program number, version number, and transaction ID. This cache avoids processing retransmitted requests that might not be idempotent. Data TypeInteger (32-bit) Default1024 Range1 to 231 - 1 UnitsRequests Dynamic?The cache is dynamically sized, but the hash queues that provide fast access to the cache are statically sized. Making the cache very large might result in long search times to find entries in the cache.Do not set the value of this parameter to 0. This value prevents the NFS server from handling non idempotent requests. ValidationNone When to ChangeExamine the value of this parameter if false failures are encountered by NFS clients. For example, if an attempt to create a directory fails, but the directory is actually created, perhaps that retransmitted MKDIR request was not detected by the server.The size of the cache should match the load on the server. The cache records non idempotent requests and so only needs to track a portion of the total requests. The cache does need to hold the information long enough to be able to detect a retransmission by the client. Typically, the client timeout for connectionless transports is relatively short, starting around 1 second and increasing to about 20 seconds. Commitment LevelUnstable DescriptionControls the size of the duplicate request cache that detects RPC- level retransmissions on connection-oriented transports. This cache is indexed by the client network address and the RPC procedure number, program number, version number, and transaction ID. This cache avoids processing retransmitted requests that might not be idempotent. Data TypeInteger (32–bit) Default1024 Range1 to 231 - 1 UnitsRequests Dynamic?Yes ValidationThe cache is dynamically sized, but the hash queues that provide fast access to the cache are statically sized. Making the cache very large might result in long search times to find entries in the cache.Do not set the value of this parameter to 0. It prevents the NFS server from handling non-idempotent requests. When to ChangeExamine the value of this parameter if false failures are encountered by NFS clients. For example, if an attempt to create a directory fails, but the directory is actually created, it is possible that a retransmitted MKDIR request was not detected by the server.The size of the cache should match the load on the server. The cache records non-idempotent requests and so only needs to track a portion of the total requests. It does need to hold the information long enough to be able to detect a retransmission on the part of the client. Typically, the client timeout for connection oriented transports is very long, about 1 minute. Thus, entries need to stay in the cache for fairly long times. Commitment LevelUnstable