Quantum 6-00360-15 manual Server Configuration, Name Description Default

Table 28 QOS Configuration Keywords

Appendix D Quality of Service Guide

Configuration

ios_sec = mb_sec /

(stripe_breadth * stripe_depth *fs_blocksize)

For example, with a file system blocksize of 4k, a stripe_breadth of 384, and a stripe_depth of four, the equivalent number of I/Os/sec for each well- formed I/O would be 216 Mb/sec / (384 * 4 * 4k). This is equivalent to 221184 k/sec / 6144k= 36 I/O/sec.

Server Configuration

All storage subsystems are different, so users must qualify the I/O subsystem and determine the maximum amount of I/O bandwidth available. SNFS relies on the correct setting in the configuration file; if the storage system changes (for example, because of a new disk array,) the user must re-qualify the I/O subsystem to determine the amount of bandwidth available. This amount will be specified in the FSM configuration file. The user can also specify the minimum amount of bandwidth to be provided to non-real-time applications.

There are five keywords controlling QOS that can be specified in the stripe group section of the FSM configuration file. Not all keywords need be present. Typically, the user specifies the RTIO bandwidth in terms of either number of I/O operations per second (rtios) or megabytes per second (rtmb). Keywords are not case sensitive.

For a minimum configuration, only the real-time limit (either rtios or rtmb) need be specified. All other configuration variables default to reasonable values.

Name	Description	Default
Rtios	The maximum number of real-	0 (no real-time)
	time I/Os allowed in a stripe
	group during any one-second
	period.
Rtmb	Maximum amount of real-time	0 (no real-time)
	MB/sec allowed on the stripe
	group during any one-second
	period.

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