HP 2000fc Hp StorageWorks 2000 Family Modular Smart Array CLI reference guide - Page 114

Parameter read-ahead-size disable|default|maximum| 64KB|128KB|256KB|512KB| 1MB|2MB|4MB|8MB|16MB|32MB Description Optional. Controls the use and size of readahead cache: • disable: Turns off read-ahead cache. This is useful if the host is triggering read ahead for what are random accesses. This can happen if the host breaks up the random I/O into two smaller reads, triggering read ahead. You can use the volume statistics read histogram to determine what size accesses the host is doing. • default: Sets one chunk for the first access in a sequential read and one stripe for all subsequent accesses. The size of the chunk is based on the chunk size used when you created the virtual disk (the default is 64 KB). Non-RAID and RAID 1 virtual disks are considered to have a stripe size of 64 KB. • maximum: Allows the controller to dynamically calculate the maximum readahead cache size for the volume. For example, if a single volume exists, this setting enables the controller to use nearly half the memory for read-ahead cache. Only use Maximum when disk drive latencies must be absorbed by cache. • 64KB, 128KB, 256KB, 512KB, 1MB, 2MB, 4MB, 8MB, 16MB, or 32MB: Sets the amount of data to read first, and the same amount is read for all read-ahead accesses. 114 HP StorageWorks 2000 Family Modular Smart Array CLI reference guide • May 2008