Data Protection; Raid Levels; Active Spare - HP StorageWorks NAS 8000 - Version 1.6.X Manual

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 NAS 8000 solution support the following RAID levels:
Note:
For additional information on RAID settings, see your storage array user's guide or search for
RAID levels at http://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.
HP StorageWorks NAS 8000 Dedicated Storage High Availability, Solution Integration Manual (SIM)
RAID 1+0. RAID 1+0 provides data redundancy and good performance. However, the
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 is a combination of RAID 1+0 and 5DP (RAID 5 Double Parity).
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.
The information for AutoRAID presented here applies to VA arrays only.
Network and Storage Planning
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