Quantum 6-00360-15 manual Monitoring, Real-time I/O available, Client Token Releases

Appendix D Quality of Service Guide

Monitoring

	to all clients that have tokens informing them of the new amount of non-
	real-time I/O available.
	While it is not a failure case, the handling of a client token release is
Client Token Releases
	exactly the same as in the case where the client disconnected. All clients
	retain non-real-time tokens for a fixed amount of time. The default is 60
	seconds. This can be controlled via the nrtiotokentimeout mount option.
	After the specified period of inactivity (i.e., no non-real-time I/O on the
	stripe group), the client will release the token back to the FSM. The FSM
	will re-calculate the amount of non-real-time bandwidth available, and
	send out callbacks to other clients.
	Therefore, if a situation exists where a periodic I/O operation occurs
	every 70 seconds, it would be beneficial to set the nrtiotokentime mount
	option to something greater than or equal to 70 seconds to cut down on
	system and SAN overhead.

Monitoring

The current real-time statistics are available via the cvadmin utility. The show long command has been enhanced to provide information as to the current limit, the minimum amount reserved for non-real-time I/O, the number of active clients, the amount currently committed, and the amount a non-real-time application could hope to get when requesting I/O.

Whenever the stripe group status changes (such as from non-real-time to real-time mode), an event is logged to syslog (system event log on Windows platforms).

On the NT platform, real-time performance is also available via the perfmon utility. There are counters for both the client (SNFS Client) and FSM (SNFS File System Server [FSS]). In the client, a number of rtio_xxx counters are available to track the number of real-time I/Os/sec, number of non-real-time I/O requests, non-real-time I/O starvation, and other counters. A full explanation of each counter is provided with the perfmon utility by clicking Explain. In the FSM, information about the number of outstanding non-real-time clients, available rtio, and other QOS information is available.

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