HP D5970A - NetServer - LCII Configuration Manual page 131

Logical Drive: A virtual drive within an array, which may consist of more than
one physical disk.
Logical drives divide up the contiguous storage space of an array of disk modules
or a spanned group of arrays of disks. The storage space in a logical drive is
spread across all the disks in the array or spanned arrays. An integrated HP
NetRAID controller can be configured with up to eight logical drives in any
combination of sizes. Configure at least one logical drive for each array.
A logical drive can be in one of five states (also see the SCSI Disk Status below):
Online: all participating disk modules are online.
Degraded: (Critical) a single disk module in a redundant array (not
RAID 0) is not online. Data loss may result if a second disk module fails.
Offline: two or more disk modules in a redundant array (not RAID 0), or
one or more disk modules in a RAID 0 array are not online.
Reconstructing: participating disk modules are being reconstructed.
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: A 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.
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.
Glossary
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