TAPECONFIG(5) AFS File Reference TAPECONFIG(5)NAMEtapeconfig - Defines parameters for tape devices and backup data files
DESCRIPTION
The tapeconfig file defines basic configuration parameters for all of
the tape devices or backup data files available for backup operations
on a Tape Coordinator machine. The file is in ASCII format and must
reside in the local /usr/afs/backup directory. The instruction for each
tape device or backup data file appears on its own line and each has
the following format:
[<capacity> <filemark_size>] <device_name> <port_offset>
where
<capacity>
Specifies the capacity of the tapes used with a tape device, or the
amount of data to write into a backup data file. The Tape
Coordinator refers to this value in two circumstances:
· When the capacity field of a tape or backup data file's label
is empty (because the tape has never been labeled). The Tape
Coordinator records this value on the label and uses it when
determining how much data it can write to the tape or file
during a backup dump or backup savedb operation. If there is
already a capacity value on the label, the Tape Coordinator
uses it instead.
· When the -size argument is omitted the first time the backup
labeltape command is used on a given tape or file. The Tape
Coordinator copies this value into the label's capacity field.
The Tape Coordinator uses this capacity value or the one on the
Backup System tape label to track how much space remains as it
writes data to a tape or backup data file. The appropriate value to
record for a tape depends on the size of the tapes usually used in
the device and whether it has a compression mode; for suggested
values, see the OpenAFS Administration Guide chapter on configuring
the Backup System. If using a value obtained from the fms command,
reduce it by 10% to 15% before recording it in the file.
For a backup data file, it is best to provide a value that helps
the Tape Coordinator avoid reaching the end-of-file (EOF)
unexpectedly. Make it at least somewhat smaller than the amount of
space available on the partition housing the file when the dump
operation begins, and never larger than the maximum file size
allowed by the operating system.
Specify a (positive) integer or decimal value followed by a letter
than indicates units, with no intervening space. In a decimal
number, the number of digits after the decimal point must not
translate to fractions of bytes. The maximum acceptable value is
2048 GB (2 TB). The acceptable units letters are as follows; if the
letter is omitted, the default is kilobytes.
· "k" or "K" for kilobytes (KB).
· "m" or "M" for megabytes (MB).
· "g" or "G" for gigabytes (GB).
· "t" or "T" for terabytes (TB).
If this field is omitted, the Tape Coordinator uses the maximum
acceptable value (2048 GB or 2 TB). Either leave both this field
and the <filemark_size> field empty, or provide a value in both of
them.
<filemark_size>
Specifies the size of a tape device's filemarks (also called end-
of-file or EOF marks), which is set by the device's manufacturer.
In a dump to tape, the Tape Coordinator inserts filemarks at the
boundary between the data from each volume, so the filemark size
affects how much space is available for actual data.
The appropriate value to record for a tape depends on the size of
the tapes usually used in the device and whether it has a
compression mode; for suggested values, see the OpenAFS
Administration Guide chapter on configuring the Backup System. If
using a value obtained from the fms command, increase it by 10% to
15% before recording it in the file.
For backup data files, record a value of 0 (zero). The Tape
Coordinator actually ignores this field for backup data files,
because it does not use filemarks when writing to a file.
Use the same notation as for the <capacity> field, but note that
the default units is bytes rather than kilobytes. The maximum
acceptable value is 2048 GB.
If this field is empty, the Tape Coordinator uses the value 0
(zero). Either leave both this field and the <capacity> field
empty, or provide a value in both of them.
<device_name>
Specifies the complete pathname of the tape device or backup data
file. The format of tape device names depends on the operating
system, but on UNIX systems device names generally begin with the
string /dev/. For a backup data file, this field defines the
complete pathname; for a discussion of suggested naming conventions
see the description of the "FILE" instruction in butc(5).
<port_offset>
Specifies the port offset number associated with this combination
of Tape Coordinator and tape device or backup data file.
Acceptable values are the integers 0 through 58510 (the Backup
System can track a maximum of 58,511 port offset numbers). Each
value must be unique among the cell's Tape Coordinators, but any
number of them can be associated with a single machine. Port offset
numbers need not be assigned sequentially, and can appear in any
order in the tapeconfig file. Assign port offset 0 to the Tape
Coordinator for the tape device or backup data file used most often
for backup operations; doing so will allow the operator to omit the
-portoffset argument from the largest possible number of backup
commands.
PRIVILEGE REQUIRED
Creating the file requires UNIX "w" (write) and "x" (execute)
permissions on the /usr/afs/backup directory. Editing the file requires
UNIX "w" (write) permission on the file.
EXAMPLES
The following example tapeconfig file configures three tape devices and
a backup data file. The first device has device name /dev/rmt/0h, and
is assigned port offset 0 because it will be the most frequently used
device for all backup operations in the cell. Its default tape capacity
is 2 GB and filemark size is 1 MB. The /dev/rmt/3h drive has half the
capacity but a much smaller filemark size; its port offset is 3. The
third device listed, /dev/rmt/4h, has the same capacity and filemark
size as the first device and is assigned port offset 2. Port offset 4
is assigned to the backup data file /dev/FILE, which is actually a
symbolic link to the actual file located elsewhere on the local disk.
The Tape Coordinator writes up to 1.5 GB into the file; as recommended,
the filemark size is set to zero.
2G 1M /dev/rmt/0h 0
1g 4k /dev/rmt/3h 3
2G 1m /dev/rmt/4h 2
1.5G 0 /dev/FILE 4
SEE ALSObackup_addhost(8), backup_dump(8), backup_labeltape(8),
backup_savedb(8), butc(8), fms(8)COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
This documentation is covered by the IBM Public License Version 1.0.
It was converted from HTML to POD by software written by Chas Williams
and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.
OpenAFS 2013-10-09 TAPECONFIG(5)
