Hitachi Compute Rack CR 210H User Manual page 32

Hot plug
If a logical drive is operating in degraded mode, the failed disk must be replaced
as soon as possible. If the system unit is shut down once at this time, it takes
more time to replace the disk. Above all, the system operation must be shut
down. It will take longer time to replace the degraded disk after turning off power
to the system unit.
A hot plug or hot swap is referred to as a function for resolving this problem,
enabling the user to replace a HDD without shutting down the system unit.
Hot spare
If a failure occurs on the logical drive of RAID1, 5, 6, or 10, the failed disk must
be replaced to return the system normal status. If a spare disk (reserve disk) is
premounted on the array controller, data can be automatically restored on the
reserve disk in case of a failure. Preparing this reserve disk so that it can be
exchanged at any time is referred to as a hot spare. A function for the array
controller to restore data automatically to the hot spare is referred to as standby
replacement.
3-10
Depending on a logical drive configuration, a hot spare might be

unavailable.
Hot spares include a "global hot spare" that becomes effective to all

the configured logical drives (RAID1, 5, 6, and 10), and a
"dedicated hot spare" that becomes effective only to one of the
configured logical drives (RAID1, 5, 6, or 10).
System Unit Functions
Hitachi Compute Rack 210H User's Guide