Snfs Tools

		StorNext File System Tuning
		The Metadata Controller System
	This setting is adjustable using the cvupdatefs utility. For more
	information, see the cvupdatefs man page.
	Example: JournalSize	16M

SNFS Tools	The snfsdefrag tool is very useful to identify and correct file extent
	fragmentation. Reducing extent fragmentation can be very beneficial

	for performance. You can use this utility to determine whether files are
	fragmented, and if so, fix them. If your files are prone to fragmentation

you should also use the FSM config file tuning options to minimize fragmentation. These global configuration settings are InodeExpandMin, InodeExpandInc, and InodeExpandMax. (For more information, see the man cvfs_config page.) The snfsdefrag man page explains the command options in greater detail.

FSM hourly statistics reporting is another very useful tool. This can show you the mix of metadata operations being invoked by client processes, as well as latency information for metadata operations and metadata and journal I/O. This information is easily accessed in the cvlog log files. All of the latency oriented stats are reported in microsecond units.

It also possible to trigger an instant FSM statistics report by setting the Once Only debug flag using cvadmin. For example:

cvadmin -F snfs1 -e ‘debug 0x01000000’ ; tail -100 /usr/ cvfs/data/snfs1/log/cvlog

The following items are a few things to watch out for:

• A non-zero value for FSM wait SUMMARY journal waits indicates insufficient IOPS performance of the disks assigned to the metadata stripe group. This usually requires reducing the metadata I/O latency time by adjusting RAID cache settings or reducing bandwidth contention for the metadata LUN. Another possible solution is to add another metadata stripe group to the file system. This will improve metadata ops performance through I/O concurrency.

• Non-zero value for FSM wait SUMMARY free buffer waits or low hit ratio for FSM cache SUMMARY buffer lookups indicates the FSM configuration setting BufferCacheSize is insufficient.

• Non-zero value for FSM wait SUMMARY free inode waits or low hit ratio for FSM cache SUMMARY inode lookups indicates the FSM configuration setting InodeCacheSize is insufficient.

StorNext File System Tuning Guide