eG Monitoring
 

Measures reported by EqlCacheStTest

Each PS Series array is composed of controllers with mirrored battery-backed caches. Cache memory in the controller enhances read and write performance, improving overall storage throughput. Streaming data can be queued into the cache to dramatically accelerate read performance.

This test monitors each controller cache in the storage device and reports its size and mode.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Cache_size Indicates the current size of this cache. GB Ideally, the value of this measure should be high. If the cache is not adequately sized, read/write performance will suffer.
Cache_mode Indicates the current mode of this cache.   This measure reports the cache mode as follows:
  • Unknown
  • Write Through
  • Write Back

When write-through cache is turned on, the RAID controller writes data straight through the cache - directly to the disks - before informing the host that the write was committed.

For performance-critical applications, the cache memory can be used to accelerate write speeds with a configuration called write-back cache. In this mode, data is considered committed, or successfully received, as soon as the controller writes back to the host that the information has been received in cache memory.

The numeric values that correspond to the above-mentioned states are as follows:

State Numeric Value
Unknown 0
Write Through 1
Write Back 2

Note:

By default, this measure reports the above-mentioned states while indicating the mode of the cache in this array. However, the graph of this measure will be represented using the corresponding numeric equivalents of the states as mentioned in the table above.