Spare Drives; Array Sizing (Capacity) - HP AD510A - StorageWorks Modular Smart Array 1500 cs 2U Fibre Channel SAN Attach Controller Shelf Hard Drive Installation Manual

Spare drives

HP recommends including spare drives in your LUNs.
Spares are hard drives that are not active members of any particular LUN, but have
been configured to be used in the event that a drive in one of the LUNs should fail.
If a spare is present and a physical hard drive fails, the spare automatically
replaces the failed drive as a member of the LUN and the process of rebuilding the
information onto the spare automatically begins. The system uses the mirrored or
parity information from the other member drives to reconstruct the data onto the
spare.

Array sizing (capacity)

When planning for optimal file serving performance, you must determine the
number of hard drives necessary to maintain an optimum performance level.
As a general rule, the greater the number of drives that are included in an array, the
greater the performance level that can be achieved. However, the performance
considerations are offset by fault tolerance considerations — the greater the
number of drives in an array, the higher the probability of one or more failures in
that array.
HP StorageWorks 1500 Modular Smart Array Installation Guide
Installation Procedures - All Deployments
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