fms - Determine a tape's capacity and a tape device's filemark size
fms -tape <
tape special file>
[
-help]
fms -t <
tape special file>
[
-h]
The
fms command determines the capacity of the tape currently in the tape
device identified by the
-tape argument, along with the size of the
filemark for the device. The filemark is also referred to as the device's
end-of-file (EOF) marker, and can differ for each combination of tape and tape
device.
As the Tape Coordinator writes a dump, it writes a filemark between the data
included from each volume and also tracks the amount of space left before the
end of the tape (EOT). For some tape devices, the filemark is large enough
(multiple megabytes) that failure to consider it leads the Tape Coordinator
significantly to overestimate the available space.
The intended use of this command is to determine tape capacity and filemark size
values that can be specified in a tape device's entry in the
/var/lib/openafs/backup/tapeconfig file. For certain types of tape
drives, the Tape Coordinator operates more efficiently when the
tapeconfig file lists accurate values. For further discussion, see the
OpenAFS Administration Guide chapter on configuring the Backup
System.
Insert a tape in the drive before issuing this command.
Do not use this command on compressing tape devices in compression mode or with
tape devices that handle tapes of multigigabyte (or multiterabyte) capacity.
It does not produce accurate results in those cases. For alternate suggestions
on the values to record in the
tapeconfig file for compressing drives,
see the
OpenAFS Administration Guide chapter on configuring the Backup
System.
Running the command completely overwrites the tape, so use a blank one or one
that can be recycled.
Because it writes filemarks to the complete length of the tape, the command can
take from several hours to more than a day to complete.
-
-tape <tape special file>
- Specifies the UNIX device name of the tape device for which
to determine filemark size and the capacity of the tape it currently
contains. The format varies on different system types, but usually begins
with /dev; an example is /dev/sd0a.
- -help
- Prints the online help for this command. All other valid
options are ignored.
The command generates output both on the standard output stream and in the
fms.log file that it creates in the current working directory. The
output reports the capacity of the tape in the device and the device's
filemark size.
The first few lines of output include status information about the execution of
the command, including such information as the number of blocks and the number
of file marks written to the tape by the command. The last two lines of both
screen and file output provide the following information:
- •
- "Tape capacity is number bytes": specifies
the size, in bytes, of the tape in the device.
- •
- "File marks are number bytes": specifies
the device's filemark size in bytes.
The following message indicates that the fms command interpreter cannot access
the tape device. The command halts.
Can't open tape drive I<device>
The following message indicates that the command interpreter cannot create the
fms.log log file. Again, the command halts.
Can't open log file
The following command illustrates the output for the device called
/dev/rmt1h:
% fms /dev/rmt1h
wrote block: 130408
Finished data capacity test - rewinding
wrote 1109 blocks, 1109 file marks
Finished file mark test
Tape capacity is 2136604672 bytes
File marks are 1910205 bytes
The following appears in the
fms.log file:
fms test started
wrote 9230 blocks
Finished file mark test
Tape capacity is 151224320 bytes
File marks are 2375680 bytes
The issuer must be able to insert and write to files in the currently working
directory, if the
fms.log file does not already exist. If it already
exists, the issuer need only be able to write to it.
fms.log(5),
tapeconfig(5)
IBM Corporation 2000. <
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