Hot spares and rebuild, Global hot spares, Hot spare operation – Dell POWERVAULT MD3600F User Manual

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Configuration: Disk Groups and Virtual Disks

Hot Spares and Rebuild

A valuable strategy to protect data is to assign available physical disks in the

storage array as hot spares. A hot spare adds another level of fault tolerance to

the storage array.
A hot spare is an idle, powered-on, stand-by physical disk ready for immediate

use in case of disk failure. If a hot spare is defined in an enclosure in which a

redundant virtual disk experiences a physical disk failure, a rebuild of the

degraded virtual disk is automatically initiated by the RAID controller

modules. If no hot spares are defined, the rebuild process is initiated by the

RAID controller modules when a replacement physical disk is inserted into

the storage array.

Global Hot Spares

The MD3600f Series supports global hot spares. A global hot spare can

replace a failed physical disk in any virtual disk with a redundant RAID level

as long as the capacity of the hot spare is equal to or larger than the size of the

configured capacity on the physical disk it replaces, including its metadata.

Hot Spare Operation

When a physical disk fails, the virtual disk automatically rebuilds using an

available hot spare. When a replacement physical disk is installed, data from

the hot spare is copied back to the replacement physical disk. This function is

called copy back. By default, the RAID controller module automatically

configures the number and type of hot spares based on the number and

capacity of the physical disks in your system.
A hot spare may have the following states:

• Standby hot spare—is a physical disk that is assigned as a hot spare and is

available to take over for any failed physical disk.

• In-use hot spare—is a physical disk that is assigned as a hot spare and is

currently replacing a failed physical disk.

book.book Page 122 Tuesday, June 18, 2013 3:03 PM

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