Quantum 3.1.4.1 manual

StorNext File System Tuning

Windows Memory Requirements

being sent to the application log and cvlog.txt about socket failures with the status code (10555) which is ENOBUFS.

The solution is to adjust a few parameters on the Cache Parameters tab in the SNFS control panel (cvntclnt). These parameters control how much memory is consumed by the directory cache, the buffer cache, and the local file cache.

As always, an understanding of the customers’ workload aids in determining the correct values. Tuning is not an exact science, and requires some trial-and-error (and the unfortunate reboots) to come up with values that work best in the customer’s environment.

The first is the Directory Cache Size. The default is 10 (MB). If you do not have large directories, or do not perform lots of directory scans, this number can be reduced to 1 or 2 MB. The impact will be slightly slower directory lookups in directories that are frequently accessed.

Also, in the Mount Option panel, you should set the Paged DirCache option.

The next parameters control how many file structures are cached on the client. These are controlled by the Meta-data Cache low water mark, Meta-

data Cache high water mark and Meta-data Cache Max water mark. Each file structure is represented internally by a data structure called the “cvnode.” The cvnode represents all the state about a file or directory. The more cvnodes that there are encached on the client, the fewer trips the client has to make over the wire to contact the FSM.

Each cvnode is approximately 1462 bytes in size and is allocated from the non-paged pool. The cvnode cache is periodically purged so that unused entries are freed. The decision to purge the cache is made based on the Low, High, and Max water mark values. The 'Low' default is 1024, the 'High' default is 3072, and the 'Max' default is 4096.

These values should be adjusted so that the cache does not bloat and consume more memory than it should. These values are highly dependent on the customers work load and access patterns. Values of 512 for the High water mark will cause the cvnode cache to be purged when more than 512 entries are present. The cache will be purged until the low water mark is reached, for example 128. The Max water mark is for situations where memory is very tight. The normal purge algorithms takes access time into account when determining a candidate to evict from the cache; in tight memory situations (when there are more than 'max' entries in the cache), these constraints are relaxed so that memory can be released. A value of 1024 in a tight memory situation should work.

26	StorNext File System Tuning Guide