Learn About Cache Settings and Performance

 is an area of temporary volatile storage (RAM) on the  that has a faster access time than the physical disk media. By using cache memory, you can increase overall I/O performance because:

• Data requested from the  for a read might already be in the cache from a previous operation, eliminating the need for physical disk access.
• Write data is written initially to the cache, which frees the application to continue instead of waiting for the data to be written to the physical disk.

To measure cache effectiveness, examine the cache hit percentage in the Performance Monitor. This value shows the percentage of data requests that are serviced by the cache and did not require a disk access.

Storage Array Cache Settings

Select Storage Array >> Change >> Cache Settings to specify, for all  in the , the:

• Start value (percentage) - When unwritten cache data should be written to disk (flushed)
• Stop value (percentage) - When a cache flush should stop
• Cache block size

When the cache holds the specified start percentage of unwritten data, a flush is triggered. When the cache flushes down to the specified stop percentage, the flush is stopped. For example, you can specify that the RAID controller module start flushing the cache when the cache reaches 80% full and stop flushing the cache when the cache reaches 16% full.

Note: Both the Start flushing and Stop flushing parameters in this version of the storage management software are percentages of the total cache memory. The Stop flushing parameter is NOT equal to the Demand Flush Amount parameter used in previous versions of this storage management software. (The Demand Flush Amount parameter was a specified percentage of the Demand Flush Threshold; neither of these parameters are currently used.)

Virtual Disk Cache Settings

Select Virtual Disk >> Change >> Cache Settings to enable or set read and , , write caching without batteries, and dynamic cache read  for a selected virtual disk.

Related Topics

Changing Storage Array Cache Settings

Changing Virtual Disk Properties

Learn About Cache Memory Protection

Monitoring Performance