Seagate ST11200N Technical Information PDF herunterladen (Seite 53)

Configuring Tape Drives

Configuring Non-QIC Tape Drives

The terms variable length block or fixed length block refer to the behavior of reads and writes

and the way the kernel packs physical tape records into logical tape records for an

application. Variable-mode devices allow more flexibility in reading previously written

tapes. Many tape devices can be accessed in either mode. NetBackup assumes variable

length for non-QIC drives.

For more information, see chdev(1), smit(1) and the system management guide. The

smit application is the most convenient way to manually change from fixed to

variable-length-block devices.

Caution Non-QIC tape drives must be configured as variable-length-block devices if

they will be used by Media Manager. Otherwise NetBackup is able to write data

but may not be able to read it correctly. During a read, you may see a “not in tar

format” error.

Automatic Configuration

When a non-QIC tape drive is configured using NetBackup, NetBackup will

automatically issue the chdev command to configure the drive as a variable length block

device. It is normally not necessary to manually run the chdev command, but the details

of the command issued by NetBackup are provided (see “Using the chdev Command” on

page 39).

Using the chdev Command

Ensure that the device being used is configured for variable mode by using the chdev

command as follows:

/usr/sbin/chdev -l

Dev

-a block_size=0

Where Dev is the logical identifier for the drive (for example: rmt0 or rmt1).

Using Extended-File Marks for Drives

Tape drives must be configured to use extended file marks, if those tape drives are capable

of supporting them (for example, 8-mm drives). See chdev(1) and smit(1) for

additional information. Otherwise, NetBackup may not be able to use those drives.

Chapter 3, IBM AIX 39

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Seagate ST11200N Technical Information Seite 53