Data Protection; Active Spare - HP StorageWorks 8000 - NAS Overview

Data Protection

RAID Levels
Redundant Array of Inexpensive Disks (RAID) technology uses different industry-standard
techniques for storing data and maintaining data redundancy. These techniques, called "RAID
levels," define the method used for distributing data on the disks in a logical unit (LUN). The
storage arrays used in the HP NAS 8000 HA solution support the following RAID levels:
RAID 1+0. RAID 1+0. RAID 1+0 provides data redundancy and good performance. However, the RAID 1+0. RAID 1+0.
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performance is achieved by using a less efficient technique of storing redundant data called
"mirroring." Mirroring maintains two sets of the data: a primary set and a backup set, or
"mirror", of the primary set. Therefore, half of the disk space is consumed by redundant
data.
AutoRAID AutoRAID. AutoRAID is a combination of RAID 1+0 and 5DP (RAID 5 Double Parity). AutoRAID AutoRAID
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RAID 5DP provides data redundancy and improves cost-efficiency by using a more efficient
method of storing redundant data. However, there is a performance penalty for each write
operation.
AutoRAID relieves you of many of the decisions regarding RAID levels and data location by
automatically selecting RAID 1+0 or RAID 5DP depending on the usage patterns of the
data. AutoRAID automatically manages your data for you, providing redundancy and high
performance with minimal involvement. This configuration eliminates the requirement for
the system administrator to understand and configure RAID levels.
For additional information on RAID settings, see your storage array user's guide or search for
RAID levels at www.hp.com.

Active Spare

The active spare feature in the storage array offers increased protection against disk failure.
An active spare ensures that the array can restore data redundancy and performance as
quickly as possible following a hard disk failure.
An active spare reserves capacity to perform a rebuild in the event of a disk failure. If you are
using disks of different capacities in your array, active spare reserves enough space to rebuild
the largest disk. As with logical volumes, the capacity reserved for the active spare is
distributed across all the disks in the array; no one physical disk contains the active spare.
Active spare is similar to the dedicated hot spare disks used in some conventional arrays.
However, those arrays let the hot spare remain idle until it is needed. This array uses the active
spare for RAID 1+0 storage until the spare is needed. This provides the added benefit of
enhancing performance while also protecting against disk failure.
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