Chapter 51 Managing Tape Drives (Tasks)

This chapter describes how to manage tape drives.

This is a list of the step-by-step instructions in this chapter.

• How to Display Tape Drive Status

• How to Retension a Magnetic Tape Cartridge

• How to Rewind a Magnetic Tape Cartridge

Choosing Which Media to Use

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 media that is used for backing up file systems and shows the storage capacity for each media. Capacity depends on the type of drive and the data being written to the tape.

Backup Device Names

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 scheme.

In general, you specify a tape drive device as shown in the following figure.

Figure 51–1 Tape Drive Device Names

If you don't specify the density, a tape drive typicallys write at its “preferred” density, which usually means the highest density the tape drive supports. Most SCSI drives can automatically sense 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.

Specifying the Rewind Option for a Tape Drive

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 no rewind option.

Specifying Different Densities for a Tape Drive

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.

The unit and density characters are shown in Backup Device Names.

Displaying Tape Drive Status

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.

How to Display Tape Drive Status

1. Load a tape into the drive you want information about.

2. Display tape drive status with the mt command.

   # mt -f /dev/rmt/n status

3. Repeat steps 1-2, substituting tape drive numbers 1, 2, 3, and so on to display information about all available tape drives.

Example—Displaying Tape Drive Status

The following example shows the status for a QIC-150 tape drive (/dev/rmt/0) and an Exabyte tape drive (/dev/rmt/1).

$ 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= 0
$ 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= 0

The 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
$ 

Handling Magnetic Tape Cartridges

If errors occur when a tape is being read, retension the tape, clean the tape drive, and then try again.

How to Retension a Magnetic Tape Cartridge

Retension a magnetic tape cartridge with the mt command.

For example:

$ mt -f /dev/rmt/1 retension
$

Do not retension non-QIC tape drives.

How to Rewind a Magnetic Tape Cartridge

To rewind a magnetic tape cartridge, use the mt command.

For example:

$ mt -f /dev/rmt/1 rewind
$

Guidelines for Drive Maintenance and Media Handling

A backup tape that cannot be read is useless. So, to clean and check your tape drives periodically 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 with the copy.

• 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 those strategies suggested in Chapter 45, 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 containing the backup date, the name of the machine and file system backed up, backup level, the tape number (1 of n, if it spans multiple volumes), plus 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.