NAME

       fms - Determine a tape's capacity and a tape device's filemark size

SYNOPSIS

       fms -tape <tape special file> [-help]

       fms -t <tape special file> [-h]

DESCRIPTION

       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.

CAUTIONS

       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.

OPTIONS

       -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.

OUTPUT

       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

EXAMPLES

       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

PRIVILEGE REQUIRED

       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.

SEE ALSO

       fms.log(5), tapeconfig(5)

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.