grio_disks - description of guaranteed I/O rates for disk devices
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
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(1M)
-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
If the line begins with the comment symbol #, the remainder of the line
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.
ggd(1M), grio(1M), grio_bandwidth(1M), hwgraph(4), grio(5).
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.
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