HP P3410A HP NetRAID 1M/2M Installation & Configuration - Page 175

Glossary • RAID 10 results when data is striped across multiple RAID 1 logical drives. • RAID 50 results when data is striped across multiple RAID 5 logical drives. Read Policy: The three Read policies for HP NetRAID are: • Read-Ahead: This is a memory caching ability that tells the adapter to read sequentially ahead of requested data and cache the further data in memory, anticipating that the further data will be requested. Read-Ahead supplies sequential data faster, but is not as effective when accessing random data. • Normal: This policy does not use the read-ahead memory caching feature. This policy is efficient when most of the data reads are random. • Adaptive: Adaptive policy causes the read-ahead feature to be used if the last two disk accesses were in sequential sectors. Ready State: A condition in which a workable hard drive is neither online nor a hot spare, and therefore is available to add to an array, or to designate as a hot spare. Rebuild: The regeneration of all data from a failed disk in a RAID level 1, 5, 10, or 50 array to a replacement disk. A disk rebuild normally occurs without interruption of application access to data stored on the logical drive. Rebuild Rate: The speed at which the rebuild operation proceeds. Each adapter is assigned a rebuild rate, which specifies the percentage of CPU resources to be devoted to rebuild operations. Reconstruct: The act of remaking a logical drive after changing RAID levels. Redundancy: See RAID Levels SAF-TE: SCSI Access Fault-Tolerant Enclosure; a processor that manages a hot-swap mass storage cage or enclosure. SCSI Channel: The HP NetRAID-1M and 2M adapters control the disk drives via SCSI buses called "channels" over which the system transfers data in Fastand-Wide, Ultra SCSI, Ultra-2 SCSI, or Ultra-3 SCSI mode. The HP NetRAID2M adapter can control two SCSI channels. The HP NetRAID-1M adapter can control one SCSI channel. 167