HP StorageWorks MSA2012i HP StorageWorks 2000 Modular Smart Array Reference Gu - Page 317

world wide name (WWN) world wide node name (WWNN) world wide port name (WWPN) write policy write-back cache write-through cache A unique 64-bit number assigned by a recognized naming authority (often via block assignment to a manufacturer) that identifies a node process or node port. (SNIA) MSA2000 Family storage systems derive WWNs from the serial numbers of controller modules and expansion modules. A globally unique 64-bit identifier assigned to each Fibre Channel node process. (SNIA) A globally unique 64-bit identifier assigned to each Fibre Channel port. (SNIA) A cache-writing strategy used to control write operations. The write policy options are CIFS write-back and write-through cache. A caching technique in which the completion of a write request is signaled as soon as the data is in cache, and actual writing to nonvolatile media occurs at a later time. Write-back cache includes an inherent risk that an application will take some action predicated on the write completion signal, and a system failure before the data is written to non-volatile media will cause media contents to be inconsistent with that subsequent action. For this reason, good write-back cache implementations include mechanisms to preserve cache contents across system failures (including power failures) and to flush the cache at system restart time. (SNIA) This is how MSA2000 Family storage systems operate. See also writethrough cache. A caching technique in which the completion of a write request is not signaled until data is safely stored on non-volatile media. Write performance with a write-through cache is approximately that of a noncached system, but if the data written is also held in cache, subsequent read performance may be dramatically improved. (SNIA) MSA2000 Family storage systems use write-through cache when writeback cache is disabled or when cache backup power is not working. See also write-back cache. Glossary 317