A global hot spare is an unused backup disk that is part of the
disk group. Hot spares remain in standby mode. When a physical disk
that is used in a virtual disk fails, the assigned hot spare is activated
to replace the failed physical disk without interrupting the system
or requiring your intervention. When a hot spare is activated, it
rebuilds the data for all redundant virtual disks that were using
the failed physical disk.
You can change the hot spare assignment by unassigning a disk and
choosing another disk as needed. You can also assign more than one
physical disk as a global hot spare.
Global hot spares must be assigned and unassigned manually. They
are not assigned to specific virtual disks. If you want to assign
a hot spare to a virtual disk (it replaces any physical disk that
fails in the virtual disk), then use the Assign and Unassign
Dedicated Hot Spare.
You should be familiar with the size requirements and other considerations
associated with hot spares.