Chapter 38 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 Determine the Type of a Tape Drive"

• "How to Show the Status of a Magnetic Tape Drive"

• "How to Retension a Magnetic Tape Cartridge"

• "How to Rewind a Magnetic Tape Cartridge"

Choosing Which Media to Use

You typically back up Solaris 2.5 systems using:

• 1/2-inch reel tape

• 1/4-inch streaming cartridge tape

• 8-mm cartridge tape

• 4-mm cartridge tape (DAT)

You can perform backups using diskettes, but this is time-consuming and cumbersome.

The media 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.

Table 38-1 shows typical media used for backing up file systems and shows the length (or storage capacity) for each.

Capacity for 4-mm cartridge tapes depends on the type of drive and the data being written to the tape.

Backup Device Names

You specify a tape or diskette drive to use for backup by supplying a logical device name. This name points to the subdirectory containing 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. Table 38-2 shows this naming scheme.

The drive writes at its "preferred" density, which usually means the highest density it supports. Most SCSI drives can automatically sense the density or format on the tape and read it accordingly.

Tape drives fall into two categories based on controller type:

• Xylogics^TM 472 for 1/2-inch rack-mounted (top-loaded) reel-to-reel drives (see Figure 38-1)

• SCSI for 1/4-inch cartridge, 1/2-inch front-loaded reel-to-reel, and 4-mm or 8-mm helical scan drives

Within the /dev/rmt subdirectory is a set of tape device files that support different output densities.

In general, you specify a tape drive device as shown in Figure 38-1.

Figure 38-1 Tape Drive Device Names

You can have both SCSI and non-SCSI tape drives on the same system.

• A SCSI controller can have a maximum of seven SCSI tape drives.

• A non-SCSI controller can have a maximum of four tape drives.

• For each drive number (X), the density character depends on the controller and drive type as described in the following paragraphs.

Table 38-3 shows the device abbreviation for different tape controllers/units and media. Note that the first character in the device abbreviation for drive number does not have to be 0 as shown, but could be 1, 2, or 3, and so on, depending on how many tape drives are attached to the system.

Rack-Mounted Non-SCSI 1/2-Inch Reel Drives

For 1/2-inch rack-mounted tape drives with either a Tapemaster or Xylogics 472 controller, substitute the density from Table 38-4 for the A variable in the device name (/dev/rmt/XA).

If you omit the density character, the tape is usually written at its highest density, not compressed.

SCSI 1/4-Inch Cartridge and 1/2-Inch Front-Loaded Reel Drives

For SCSI 1/4-inch cartridge and 1/2-inch front-loaded reel drives, substitute the density from Table 38-5for the A variable in the device name (/dev/rmt/XA).

For 1/4-inch cartridges, density is specified by the format in which the data is written: the QIC format. The QIC-11 and QIC-24 format write approximately 1000 bytes per inch on each track. The density for QIC-150 is somewhat higher. The "preferred" density for a 60-Mbyte 1/4-inch cartridge drive is QIC-24 and for a 150-Mbyte 1/4-inch cartridge drive is QIC-150.

An 18-track drive can write only QIC-150; it cannot be switched to write QIC-24 or QIC-11. Format selection is only useful for drives that can write both QIC-24 and QIC-11.

Specifying the Default Density for a Tape Drive

Normally, you specify a tape drive by its logical unit number, which may run from 0 to n. Table 38-6 describes how to specify tape device names using default density settings.

By default, the drive writes at its "preferred" density, which is usually the highest density it supports. If you do not specify a tape device, the command writes to drive number 0 at the default density the device supports.

Specifying Different Densities for a Tape Drive

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. Table 38-7 describes how to specify different densities for a tape drive.

The unit and density characters are shown in Figure 38-1.

Determining Tape Drive Types

You can use the status option with the mt command to get status information about the Xylogics 472 1/2-inch tape drive and the Exabyte EXB-8200 8-mm tape drive.

The mt command also reports information about these 1/4-inch tape drives:

• Xylogics 472

• Exabyte EXB-8200

• Sysgen (QIC-24)

• Emulex MT-02 (QIC-24)

• Archive QIC-150

• Wangtek QIC-150

How to Determine the Type of a Tape Drive

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

2. Display tape drive information 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--Determining the Type of a Tape Drive

This example shows 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

Here is an quick way to poll a system and locate all tape drives. In this example, the tape drive is at 0.

$ 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
$ 

How to Show the Status of a Magnetic Tape Drive

To display tape drive status information, use the mt command.

$ mt -f /dev/rmt/n status

Status for the tape drive you specify is displayed.

Examples--Showing the Status of a Magnetic Tape Drive

In the following example, there is no tape in drive /dev/rmt/1.

$ mt -f /dev/rmt/1 status
/dev/rmt/1: no tape loaded or drive offline
$

In this example, the status is shown for the tape in drive /dev/rmt/1.

$ mt -f /dev/rmt/1 status
Archive QIC-150 tape drive:
   sense key(0x6)= unit attention   residual= 0   retries= 0
   file no= 0   block no= 0
$

Handling Magnetic Tape Cartridges

If errors occur when reading a tape, 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.

$ mt -f /dev/rmt/n retension
 

Example--How to Retension a Magnetic Tape Drive

In this example, the tape in drive /dev/rmt/1 is retensioned.

$ 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.

$ mt -f /dev/rmt/n rewind

Example--Rewinding a Magnetic Tape Cartridge

In this example, the tape in drive /dev/rmt/1 is rewound.

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

Guidelines for Drive Maintenance and Media Handling

A backup tape that cannot be read is useless. It is a good idea 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:

• Copying some files to the tape, reading them back, and then comparing the original with the copy.

• Or, you could use 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 have planned a backup strategy similar to those suggested in Chapter 33, 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.