grio_disks(4)

NAME
     grio_disks - description of guaranteed I/O rates for disk devices

DESCRIPTION
     The /etc/grio_disks file contains information describing the I/O rates
     for individual types of disk drives.

     The entries are of the form:
          ADD "xxxxxxxxxxxxxxxxxxxxxxxxxxxx" iosize numios
     or
          REPLACE nodename iosize numios

     The first string on each line of the file must be one of the keywords
     ADD, REPLACE or the symbol for a comment line, #.

     If the line begins with the keyword ADD, the next item is the 28
     character string identifying a particular type of disk drive.  This is
     also known as the disk drive ID string.  Drives recommended by Silicon
     Graphics usually have "SGI" string as the first three characters in this
     string.  The next number describes the optimal I/O size in bytes for the
     disk device.  The final number is the number of optimal sized I/O
     requests that can be performed by the disk drive each second.

     If the line begins with the keyword REPLACE, the next item indicates a
     node name in the hwgraph or disk alias format (as reported by grio -P)
     The third and fourth values on the line indicate the optimal I/O size and
     the number of I/O operations per second, respectively.  The system
     administrator may set the bandwidth values for any node in the system.
     Specifically, REPLACE lines may be added to the /etc/grio_disks file for
     the RAID controllers and the RAID lun devices.

     Normally the optimal I/O size of a disk device used in the GRIO subsystem
     is set to the stripe width of the XLV realtime subvolume that contains
     the disk.  The system administrator may override this value for a given
     disk by using the REPLACE keyword.  If the XLV realtime subvolume is not
     striped, and REPLACE has not been used to specify an optimal I/O size,
     the disk device is given the optimal I/O size specified to ggd with the
     -o option.

     If the line begins with the comment symbol #, the remainder of the line
     is ignored.

     The performance characteristics for the supported disk drives using
     optimal I/O sizes of 64k, 128k, 256k, and 512k bytes are listed in the
     /etc/grio_disks file.  If the system administrator wants to use a
     different disk drive or a different optimal I/O size on an existing
     drive, new lines can be added to the end of the file.  The
     grio_bandwidth(1M) utility can be used to help determine the number of
     I/Os of a given size that can be supported by a given drive every second.
     After the /etc/grio_disks file is updated, the ggd daemon must be
     restarted to make use of the new configuration.

FILES
     /etc/grio_disks

SEE ALSO
     ggd(1M), grio(1M), grio_bandwidth(1M), hwgraph(4), grio(5).

NOTES
     The number of optimal sized I/O requests that can be guaranteed each
     second may be significantly less than the maximum performance of the
     drive.  This is because each request is considered to be distinct and may
     require a maximum length seek before the request is issued.

     Entries created by grio_bandwidth may assume that the RAID controller is
     on lun0, even if lun0 is a regular disk lun.  ggd needs to allocate
     bandwidth to a device for the controller, and lun0 is chosen simply for
     the sake of convenience.  This configuration is normal and expected, and
     should not cause any conflicts or other problems.

     The guaranteed rate I/O capabilities described in this man page refer to
     the version one GRIO implementation. Refer to grio2(5) for information
     covering the newer GRIO Version 2 implementation which supports both
     local and clustered XVM volumes.