HP 2000fc Hp StorageWorks 2000 Family Modular Smart Array CLI reference guide - Page 112

Independent Cache Performance Mode In the storage system's default operating mode, Active-Active, data for volumes configured to use write-back cache is automatically mirrored between the two controllers. Cache redundancy has a slight impact on performance but provides fault tolerance. You can disable cache redundancy, which permits independent cache operation for each controller; this is called independent cache performance mode (ICPM). The advantage of ICPM is that the two controllers can achieve very high write bandwidth and still use write-back caching. User data is still safely stored in nonvolatile RAM, with backup power provided by super-capacitors should a power failure occur. This feature is useful for high-performance applications that do not require a fault-tolerant environment for operation; that is, where speed is more important than the possibility of data loss due to a drive fault prior to a write completion. The disadvantage of ICPM is that if a controller fails, the other controller will not be able to fail over (that is, take over I/O processing for the failed controller). If a controller experienced a complete hardware failure, and needed to be replaced, then user data in its write-back cache is lost. Caution - Data might be compromised if a RAID controller failure occurs after it has accepted write data, but before that data has reached the disk drives. Do not use ICPM in an environment that requires fault tolerance. Note - Independent cache performance mode disables partner firmware upgrade. Controllers must be upgraded manually. The operating mode applies per storage system, not per volume. Input To set cache options for a volume: set cache-parameters volume [write-policy write-back| write-through] [optimization standard|super-sequential] [read-ahead-size disable|default|maximum|64KB|128KB|256KB|512KB| 1MB|2MB|4MB|8MB|16MB|32MB] 112 HP StorageWorks 2000 Family Modular Smart Array CLI reference guide • May 2008