HP Array Controller HSG V8.7 Software - Manual (Page 357)

CLI Commands B–85
REDUCE
Removes member disk drives from mirrorsets and decreases the
nominal number of members in the mirrorsets.
Unlike the SET mirrorset-name REMOVE=disk-name command, the
controller does not put reduced members into the failedset. When using
the REDUCE command to take a snapshot of a striped mirrorset, you
must reduce all mirrorsets with one command. The CLONE utility does
this automatically.
The nominal number of members in a mirrorset is determined by the
number of members assigned to the mirrorset with the SET mirrorset-
name MEMBERSHIP=number-of-members command or the ADD
MIRRORSET mirrorset-name disk-name1 [disk-nameN] command—in
other words, the number of disks that the mirrorset originally contained
before it was reduced. The actual number of members contained in the
mirrorset may be less than the nominal number of members if:
n A disk drive is not added back to the mirrorset
n A member remains removed from the mirrorset
n The mirrorset replacement policy switch NOPOLICY is specified
with the SET mirrorset-name command
n No spare disks exist
The actual number of members in the mirrorset can never be greater
than the nominal number of members. The disks to be removed do not
need to be members of the same mirrorset. However, the disks must all
be part of the same unit (for example, the same striped mirrorset).
When a disk is reduced from a mirrorset, the controller:
n Pauses I/O to the unit
n Flushes all of the unit's data from write-back data cache
n Removes the specified disk(s)
n Decreases the nominal number of members of the mirrorset(s) by
the number of disk(s) removed from the mirroset(s).
For each reduced mirrorset, there must be at least one remaining normal
member after the reduction. If this is not true for all of the disk-names
specified, the mirrorset is not reduced.