HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 393

Class of Service The types of services provided by the Fibre Channel topology and used by the communicating port. controller A removable unit that contains an array controller. dacstore A region on each disk used to store configuration information. During the Start Of Day process, this information is used to configure controller NVSRAM and to establish other operating parameters, such as the current LUN configuration. data redundancy The technique of storing extra data along with the original data to protect against a disk failure. This extra, or redundant, data is used to rebuild the original data if a disk fails or becomes inaccessible. Data redundancy is achieved using one of two techniques: mirroring or parity. data transfer rate Data transfer rate is the speed at which data is transferred between a host computer system and a peripheral. degraded mode The operating mode a LUN enters when if a disk fails or becomes inaccessible. In degraded mode the LUN must recreate the data on the missing disk using either mirrored data or parity information. I/O performance typically suffers while the LUN is in degraded mode. In addition, the LUN is susceptible to a second disk failure while in degraded mode. The LUN will remain in degraded mode until the content of the failed disk is rebuilt to a global hot spare or a replacement disk. DIMM Dual-inline memory module. 393 Glossary