HP Surestore Disk Array 12h - And FC60 Service Manual page 262

Glossary
Auto Rebuild
Availability
Balancing
Block Mirroring
Cache
Channel
Configuration
Data Redundancy
262
Auto Rebuild begins immediately if a disk failure occurs, as long as
enough space is available to perform the rebuild. No operator
intervention is required to perform an Auto Rebuild. Once the Auto
Rebuild has completed, the disk array is once again Fault-tolerant,
since all user data is once again redundant.
Availability is achieved by using redundant data to prevent the loss of
use of a storage system in the event of a disk failure.
Balancing is the process of automatically spreading data equally across
all disks to increase performance. When a fixed amount of data is either
written or read from multiple disks instead of to or from just one disk,
the throughput or speed of the process increases greatly.
Block Mirroring is a technique in which duplicate copies of blocks of
data are stored on an array of disks.
An on-board cache, or memory buffer, greatly enhances the speed of
data transfers to and from disk devices, since the next block of data
required by the host computer is often already available in high-speed
cache memory. Caching does require controller overhead, however, so
unlike traditional RAID systems that often utilize huge cache space, the
disk array is tuned with an optimum cache. The disk array contains
SIMMs with Error Correction Code (ECC), which are capable of both
error detection and correction on the Disk Array Controller. Most RAID
systems use SIMMs without ECC.
A Channel refers to a SCSI bus on the Disk Array Controller. Each
Disk Array Controller is connected to one channel.
See Auto Configuration and Self Configuring.
Data Redundancy protects the disk array from lost data if a disk fails.
With Data Redundancy, the array can reconstruct the data that was on
the failed disk. If a disk fails, Data Redundancy is lost until the array
rebuilds the data that was on the failed disk.