Measures reported by PzStatCacheTest

Panzura CloudFS utilizes a user-definable percentage of the local storage as the SmartCache to track hot, warm, and cold file block structures as they are accessed. This form of caching increases the I/O performance of reads by servicing them from local cached storage rather than from external cloud storage. Caching policies provide two basic functions. The first function is pinned data, which keeps data available on local storage using flexible wildcard policy rules. Pinning is a forced action and executed against full files whereas SmartCache is a read-stimulated action executed against frequently accessed blocks within a file. The second function provided by caching policies is Auto-Caching which automatically caches data locally based on defined rules. Auto-cached data can be evicted for requested hot data, as needed. The pinned, or auto-cached, data is a subset of the total SmartCache storage tier. Pinned data is considered high-priority cached data that is never evicted unless authorized by the administrator, whereas auto-cached (cached based on wildcard rules) or SmartCache cached (data blocks automatically cached based on observed usage patterns) can be evicted by the system if needed to make space for more frequently accessed data.

As more pinned data consumes the local space, the usable auto-cache capacity is reduced. This will negatively impact the most frequently read data, causing it to be evicted and then re-read continuously. Therefore, aggressive policies that pin large amounts of data should be used sparingly as this could cause excessive local disk I/O and reduce performance. Also, over consumption of local space by pinned data causes inefficient local cache utilization leading to less or no space for actual hot data. Therefore, it is imperative to keep an eye on the number of cache hits and misses of pinned, auto-cached and evicted data for ensuring efficient perfromance of the appliance. The PzStatCacheTest helps administrators in this regard!

This test monitors the local storage of the target appliance and reports the number of cache hits and misses with pinned and auto-cached data in the local cache. This way administratrors can easily identify when the amount of pinned data increases beyond the permissible limit over-riding the auto-cached data. This test also keeps a track on the number of cache misses, thereby shedding light on the unavailability of hot pinned or auto-cached data. In addition, this test also promptly alert administrator on the number of evictions from the local cache, thus helping them to proactively resolve any potential perfromance issues before it affects the user experience.

Outputs of the test: One set of results for the target appliance being monitored.

The measures made by this test are as follows: