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grio_disks(4)							 grio_disks(4)

NAME    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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
     -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.

									Page 1

grio_disks(4)							 grio_disks(4)

     After the /etc/grio_disks file is updated,	the ggd	daemon must be
     restarted to make use of the new configuration.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

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

NOTE    [Toc]    [Back]

     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.

									PPPPaaaaggggeeee 2222
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