This chapter describes how to manage tape drives in the Solaris Operating System (Solaris OS).This is a list of the step-by-step instructions in this chapter.How to Display Tape Drive Status Retensioning a Magnetic Tape Cartridge Rewinding a Magnetic Tape Cartridge This is a list of overview information in this chapter.Choosing Which Media to Use Backup Device Names Displaying Tape Drive Status Guidelines for Drive Maintenance and Media Handling You typically back up Solaris systems by using the following tape media:1/2-inch reel tape 1/4-inch streaming cartridge tape 8-mm cartridge tape 4-mm cartridge tape (DAT) You can perform backups with diskettes, but doing so is time-consuming and cumbersome.The media that you choose depends on the availability of the equipment that supports it and of the media (usually tape) that you use to store the files. Although you must do the backup from a local system, you can write the files to a remote device. The following table shows typical tape devices that are used for backing up file systems. The storage capacity for each device depends on the type of drive and the data being written to the tape.Backup Media Storage Capacity 1/2-inch reel tape 140 Mbytes (6250 bpi) 2.5-Gbyte 1/4-inch cartridge (QIC) tape 2.5 Gbytes DDS3 4-mm cartridge tape (DAT) 12–24 Gbytes 14-Gbyte 8-mm cartridge tape 14 Gbytes DLT 7000 1/2-inch cartridge tape 35–70 Gbytes You specify a tape or diskette to use for backup by supplying a logical device name. This name points to the subdirectory that contains the “raw” device file and includes the logical unit number of the drive. Tape drive naming conventions use a logical, not a physical, device name. The following table shows this naming convention.Device Type Name Tape /dev/rmt/n Diskette /vol/dev/rdiskette0/unlabeled In general, you specify a tape device as shown in the following figure.

Illustration shows logical tape device name that includes magnetic tape device directory, drive, and the optional density values.

If you don't specify the density, a tape drive typically writes at its “preferred” density. The preferred density usually means the highest density the tape drive supports. Most SCSI drives can automatically detect the density or format on the tape and read it accordingly. To determine the different densities that are supported for a drive, look at the /dev/rmt subdirectory. This subdirectory includes the set of tape device files that support different output densities for each tape.Also, a SCSI controller can have a maximum of seven SCSI tape drives.Normally, you specify a tape drive by its logical unit number, which can run from 0 to n. The following table describes how to specify tape device names with a rewind or a no-rewind option.Drive and Rewind Value Use This Option First drive, rewind /dev/rmt/0 First drive, no rewind /dev/rmt/0n Second drive, rewind /dev/rmt/1 Second drive, no rewind /dev/rmt/1n By default, the drive writes at its “preferred” density, which is usually the highest density the tape drive supports. If you do not specify a tape device, the command writes to drive number 0 at the default density the device supports.To transport a tape to a system whose tape drive supports only a certain density, specify a device name that writes at the desired density. The following table describes how to specify different densities for a tape drive.Drive, Density, and Rewind Value Use This Option First drive, low density, rewind /dev/rmt/0l First drive, low density, no rewind /dev/rmt/0ln Second drive, medium density, rewind /dev/rmt/1m Second drive, medium density, no rewind /dev/rmt/1mn The additional density values are shown in Backup Device Names. You can use the status option with the mt command to get status information about tape drives. The mt command reports information about any tape drives that are described in the /kernel/drv/st.conf file.Load a tape into the drive you want information about. Display the tape drive status.# mt -f /dev/rmt/n status Repeat steps 1–2, substituting tape drive numbers 0, 1, 2, 3, and so on to display information about all available tape drives. The following example shows the status for a QIC-150 tape drive (/dev/rmt/0):$ mt -f /dev/rmt/0 status Archive QIC-150 tape drive: sense key(0x0)= No Additional Sense residual= 0 retries= 0 file no= 0 block no= 0The following example shows the status for an Exabyte tape drive (/dev/rmt/1):$ mt -f /dev/rmt/1 status Exabyte EXB-8200 8mm tape drive: sense key(0x0)= NO Additional Sense residual= 0 retries= 0 file no= 0 block no= 0The following example shows a quick way to poll a system and locate all of its tape drives: $ for drive in 0 1 2 3 4 5 6 7 > do > mt -f /dev/rmt/$drive status > done Archive QIC-150 tape drive: sense key(0x0)= No Additional Sense residual= 0 retries= 0 file no= 0 block no= 0 /dev/rmt/1: No such file or directory /dev/rmt/2: No such file or directory /dev/rmt/3: No such file or directory /dev/rmt/4: No such file or directory /dev/rmt/5: No such file or directory /dev/rmt/6: No such file or directory /dev/rmt/7: No such file or directory $ If errors occur when a tape is being read, you can retension the tape, clean the tape drive, and then try again.Retension a magnetic tape cartridge with the mt command.For example:$ mt -f /dev/rmt/1 retension $Do not retension non-QIC tape drives. To rewind a magnetic tape cartridge, use the mt command.For example:$ mt -f /dev/rmt/1 rewind $ A backup tape that cannot be read is useless. So, periodically clean and check your tape drives to ensure correct operation. See your hardware manuals for instructions on procedures for cleaning a tape drive. You can check your tape hardware by doing either of the following:Copying some files to the tape, reading the files back, and then comparing the original files with the copied files. Using the v option of the ufsdump command to verify the contents of the media with the source file system. The file system must be unmounted or completely idle for the v option to be effective. Be aware that hardware can fail in ways that the system does not report.Always label your tapes after a backup. If you are using a backup strategy similar to the strategies suggested in Chapter 23, Backing Up and Restoring File Systems (Overview), you should indicate on the label “Tape A,” “Tape B,” and so forth. This label should never change. Every time you do a backup, make another tape label that contains the following information:The backup date The name of the machine and file system that is backed up The backup level The tape number (1 of n, if the backup spans multiple volumes) Any information specific to your site Store your tapes in a dust-free safe location, away from magnetic equipment. Some sites store archived tapes in fireproof cabinets at remote locations. You should create and maintain a log that tracks which media (tape volume) stores each job (backup) and the location of each backed-up file.