Glossary
array
A set of physical disks configured into logical drives. Arrayed disks have significant performance
and data protection advantages over nonarrayed disks.
array accelerator
A component of some Smart Array Series controllers that dramatically improves disk read and
write performance by providing a buffer. Data integrity is protected by a backup battery and
ECC memory.
array capacity
expansion
See capacity expansion.
Array
Configuration
Utility (ACU)
A configuration utility useful for novices and experienced RAID users.
Array Diagnostic
Utility (ADU)
A diagnostic tool that collects comprehensive information about array controllers in a server and
lists any problems detected.
Auto-Reliability Monitoring (ARM)
Also known as surface analysis. A fault management feature that scans physical disks for bad
sectors. Data in the faulty sectors remaps to good sectors. Also checks parity data consistency
for disks in RAID 5 or RAID ADG configurations. Operates as a background process.
Automatic Data
Recovery
A process that reconstructs data from a failed disk and writes it to a replacement disk. Automatic
Data Recovery time depends on several factors, but you should allow at least 15 minutes per
gigabyte. Also known as rebuild.
cache
A high-speed memory component used to store data temporarily for rapid access.
capacity expansion
The addition of physical disks to an existing disk array, and the redistribution of existing logical
drives and data over the enlarged array. The size of the logical drives does not change. Also
known as an array capacity expansion.
capacity extension
The enlargement of a logical drive without disruption of data. Before capacity extension can
occur, there must be free space in the array. If necessary, create free space by deleting a logical
drive or by carrying out a capacity expansion. Also known as a logical drive capacity extension.
CISS
Command Interface for SCSI-3 Support Specification.
controller
duplexing
A type of fault tolerance that requires two Smart Array Series controllers. Each controller has its
own set of disks, and the disk sets have identical data. When one controller fails, the other takes
over the servicing of requests. Controller duplexing can be done with LVM MirrorDisk/UX.
data guarding
See RAID.
data striping
Writing data to logical drives in interleaved chunks (by byte or by sector). Data striping improves
system performance.
drive mirroring
See RAID.
Error Correction
and Checking
(ECC) memory
A type of memory that checks and corrects single-bit or multibit memory errors (depending on
configuration) without causing the server to halt or to corrupt data.
fault tolerance
The ability of a server to recover from hardware problems without interrupting server performance
or corrupting data. Hardware RAID is most commonly used, but there are other types of fault
tolerance, including controller duplexing and software-based RAID.
flashing
Updating the flash memory on a system. Flash memory is nonvolatile memory used to hold control
code such as BIOS information. Flash memory is very fast because it can be rewritten block by
block, rather than byte by byte.
hot spare
See online spare.
interim data
recovery
If a disk fails in RAID 1, 1+0, 5, or ADG, the system still processes I/O requests, but at a reduced
performance level.
logical drive
A group of physical disks, or part of a group, that behaves as one storage unit. Each constituent
physical disk contributes the same storage volume to the total volume of the logical drive. A logical
drive has performance advantages over individual physical disks. Also known as a logical volume.
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