HP NetRAID 1Si Controller - Manual (Page 152)

Glossary
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Reconstructing: Participating disk modules are being reconstructed.
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Rebuilding: Participating disk modules are being rebuilt.
I/O operations can only be performed with logical drives that are online or
degraded (critical).
Logical Volume: An array virtual disk made up of logical disks rather than
physical ones. Also called a partition.
MB: A megabyte; an abbreviation for 1,048,576 (2 to the 20th power) bytes; used
for memory or disk capacities.
Mirroring: The style of redundancy in which the data on one disk completely
duplicates the data on another disk. RAID levels 1 and 10 use mirroring.
Online Capacity Expansion: Capacity expansion by adding volume or another
hard drive without restarting the HP NetServer.
Parity: Parity is an extra bit added to a byte or word to reveal errors in storage (in
RAM or disk), or transmission. It is used to generate a set of redundancy data
from two or more parent data sets. The redundancy data can be used to reconstruct
one of the parent data sets; however, parity data do not fully duplicate the parent
data sets. In RAID, this method is applied to entire drives or stripes across all disk
drives in an array. Parity consists of Dedicated Parity, in which the parity of the
data on two or more disks is stored on an additional disk, and Distributed Parity,
in which the parity data are distributed among all the disks in the system. If a
single disk fails, it can be rebuilt from the parity of the respective data on the
remaining disks.
Partition: An array virtual disk made up of logical disks rather than physical
ones. Also called logical volume.
Physical Drive: In HP NetRAID, a disk drive.
Physical Disk Roaming: The ability of an adapter to keep track of a hot-swap
disk module that has been moved to a different slot in the hot-swap cages. Both
slots must be controlled by the same HP NetRAID Series adapter or integrated
HP NetRAID controller.
RAID: Redundant Array of Independent Disks (originally Redundant Array of
Inexpensive Disks) is an array of multiple small, independent hard disk drives that
yields performance exceeding that of a Single Large Expensive Disk (SLED). A
RAID disk subsystem improves I/O performance using only a single drive. The
RAID array appears to the host HP NetServer as a single storage unit. I/O is
expedited because several disks can be accessed simultaneously.