HP LH4r Installation and configuration of the HP NetRAID, NetRAID-1 and NetRAI - Page 141
RAID 5, RAID 10, RAID 30, RAID 50, Read Policy, Read-Ahead, Normal, Adaptive, Ready State, Rebuild,
View all HP LH4r manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 141 highlights
Glossary • RAID 5 has parity redundancy distributed over all the disks in the array. It requires three or more physical drives in an array. RAID levels 10, 30, and 50 result when logical drives span arrays. Table 2-2 in Chapter 2 describes RAID levels for logical drives that span arrays. • RAID 10 results when a RAID 1 logical drive spans arrays. • RAID 30 results when a RAID 3 logical drive spans arrays. • RAID 50 results when a RAID 5 logical drive spans arrays. 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, 3, 5, 10, 30, 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 SCSI Channel: The HP NetRAID Series adapters control the disk drives via SCSI-2 buses called "channels" over which the system transfers data in Fast-andWide, Ultra SCSI, or Ultra-2 SCSI mode. Each HP NetRAID adapter can control up to three SCSI channels. Each HP NetRAID-1 adapter can control one SCSI channel. 133