The HP 3PAR Operating System has a logical volume manager
that handles volume abstraction at the Virtual Volume layer and also handles
sparing. This logical volume manager reserves a certain number of chunklets as
spare chunklets depending on the sparing algorithm and system configuration.
Unlike many competitive arrays that reserve dedicated spare drives that then
sit idle, system-wide sparing with HP 3PAR StoreServ Storage means that spare
chunklets are distributed across all drives. This provides additional
protection and enables a balanced load that extends the SSD lifespan by
providing even wearing. It also protects against performance degradation by
enabling a “many-to-many” rebuild in the event of a failure. After the jump I
have listed a few CLI commands to check the system-wide sparing algorithm in
use and how to change it.
showpd -c -p -devtype “disk type (example FC,
Displays all of the disks of the selected type
and shows what each chunklet is doing. Look for the “Free” column under the
Spare Chunklets section. This tells you the amount of chunklets being dedicated
for sparing on each disk.
Displays the sparing algorithm currently in use.
In this case the Default setting is selected.
setsys SparingAlgorithm “setting”
Sets the sparing algorithm. You have 3 options
to choose from.
1x biggest disk size worth of chunklets per 24 drives with no minimum
1x biggest disk size worth of chunklets per 24 drives with an enforced 2 disk
1x biggest disk size worth of chunklets per installed type per enclosure
Example: setsys SparingAlgorithm Default