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grio_bandwidth(1M)					    grio_bandwidth(1M)

NAME    [Toc]    [Back]

     grio_bandwidth - determines guaranteed-rate I/O device bandwidth

SYNOPSIS    [Toc]    [Back]

     grio_bandwidth -d device -s iosize	[ -ruwV	] [ -t sampletime ]
     grio_bandwidth -c controller -s iosize [ -ruwV ] [	-t sampletime ]
     grio_bandwidth -R -s iosize [ -fruwV ] [ -t sampletime ]

DESCRIPTION    [Toc]    [Back]

     grio_bandwidth is used to determine the number of I/O operations of a
     given size	that can be guaranteed to be performed by a given disk device,
     RAID subsystem or SCSI controller in one second.  It creates processes
     which repeatedly issue I/O	requests of the	given size, and	device seeks
     of	random lengths,	to the specified devices.  The length of time to
     complete each request is recorded and this	information is used to
     determine the average number of I/O operations that were performed	by the
     device per	second over the	sample period.	This number is degraded	by 10%
     to	provide	an approximation of the	increase in I/O	response time caused
     by	a  heavily loaded system.  In addition,	grio_bandwidth keeps track of
     the longest time to complete an I/O operation time	over the sample	period
     and calculates the	number of such "worst case" operations that can	be
     performed each second.  The system	administrator can use grio_bandwidth
     to	obtain the bandwidth information needed	to create new entries in the
     Guaranteed	Rate I/O device	bandwidth information file /etc/grio_disks.

     The -d option is used to specify a	single disk device. The	disk name
     could be specified	in the /dev/[r]dsk alias name format, or in the	format
     reported back by -P, -C and -F options of the grio(1M) command.  The -c
     option is used to specify a single	SCSI controller	name. The name has to
     be	specified in the format	reported back by -P, -C	and -F options of the
     grio(1M) command. This is also the	same format used in
     /etc/ioconfig.conf.  The -R option	will cause the utility to scan for all
     RAID devices attached to the system.  The -s option is used to specify
     the size of the I/O operation in bytes. It	must be	specified, there is no
     default value.  The -t option is used to specify the length of the	sample
     period in seconds.	By default the sample period has a length of 10
     minutes.  If the -u option	is specified, the /etc/grio_disks file will be
     automatically updated with	the device bandwidth information.  The -f
     option can	only be	used when both the -R and-u options are	used. It
     indicates that when creating the entries in the /etc//grio_disk file, the
     RAID controller bandwidth should be split evening among all RAID luns
     attached to the controller. By default, the RAID controller bandwidth
     will be allocated to individual RAID luns on a first-come,	first-served
     basis.  The user can use the -r and -w options to specify if device read
     and/or write operations should be performed.  By default only read
     operations	will be	performed on the device.  Normally, both -r and	-w
     should be specified so that the utility uses a mix	of read	and write
     operations	when determining the bandwidth characteristics.	 If it is
     known that	on the device most Guaranteed Rate I/O rate guarantees will be
     used for performing either	read or	write operations, then the correct
     option may	be specified to	obtain a more accurate bandwidth
     characterization for the expected workload.  The -V option	causes the

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grio_bandwidth(1M)					    grio_bandwidth(1M)

     utility to	produce	more verbose output.  The utility will use these
     values to determine the bandwidth performance characteristics of the
     device.  In the case of a single disk device, the performance
     characteristics of	the device will	be computed.  In the case of a RAID
     device, the performance characteristics of	the RAID controllers, as well
     as	the RAID luns, will be computed.

NOTES    [Toc]    [Back]

     There are a number	of factors to consider when using grio_bandwidth to
     determine the GRIO	bandwidth characteristics of a RAID device.  First,
     the grio_bandwidth	utility	invokes	the raidcli(5) utility to determine
     the RAID devices attached to the system.  In order	to run the raidcli
     program successfully, the system must be a	registered RAID	agent.
     Second, it	is important to	re-run the utility each	time the RAID device
     is	reconfigured.  The RAID	device is a complex mechanism and
     configuration changes will	have performance impact.  Morover, in order to
     insure that the GRIO bandwidth rate guarantees can	be met even when a
     RAID disk has failed, the bandwidth number	must be	computed when the
     device is in degraded mode.  When running in degraded mode	(ie. one of
     the disk devices in each of the RAID luns is removed/missing), the	RAID
     controllers on the	RAID must compute the data for the missing disk.  This
     will increase I/O request response	time.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     ggd(1M), grio(1M),	grio_disks(4), grio(5),	raidcli(5), ioconfig(1M).

									PPPPaaaaggggeeee 2222
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