HP P3410A - NetRAID 1M RAID Controller Installation And Configuration Manual page 174

Hp netraid 1m/2m installation & configuration
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Glossary
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.
Physical Disk Roaming: The ability of a controller 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 controller.
Power Fail Safeguard: When this setting is enabled, during a reconstruction
process (not a rebuild) a copy of the data that is being restructured will always be
stored on disk, so that if a power failure occurs during the reconstruction, there
will be no risk of data loss.
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.
RAID Levels: A style of redundancy applied to a particular logical drive. It may
increase the fault tolerance and performance of the logical drive, and it may
decrease its usable capacity. Each logical drive must have a RAID level assigned
to it.
RAID levels 1 and 5 are for logical drives that occupy a single array (basic
array). Table 2-1 in Chapter 2 describes RAID levels for logical drives that do
not span arrays. Briefly,
RAID 0 has no redundancy. It requires one or more physical drives.
RAID 1 has mirrored redundancy. It requires two physical drives in an
array.
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 and 50 result when logical drives span arrays. Table 2-2 in
Chapter 2 describes RAID levels for logical drives that span arrays.
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