HP Surestore Disk Array 12h and FC60 - Manual (Page 306)

306 Managing the Disk Array Using Array Manager 60
• amount identifies the number of blocks to rebuild at a time. This value can be from 1 to
64
K
and specifies the number of 512-byte blocks processed during each rebuild
command. The higher the setting, the more blocks that will be processed, reducing I/O
performance. A lower setting gives priority to host I/Os, delaying the completion of the
rebuild. The default value for this setting is 64 blocks, or 32
K
bytes of data.
Command Example
The following example assigns a value of 5 seconds to the rebuild command rate, and sets
the data block amount to 16 blocks on LUN 4 on disk array 0000005EBD20. This gives host
I/Os higher priority than the default settings.
amutil -R 4 -f 5 -a 16 0000005EBD20
Performing a Parity Scan
To verify the integrity of the parity data on a LUN, you can perform a parity scan. This will
check each block of data against its parity to ensure that they match.
Like a rebuild, a parity scan competes with host I/Os for disk resources, and can impact
host I/O performance. The rebuild priority
amount setting is used when performing a
parity scan. A larger amount value may have a greater impact on I/O performance. To avoid
impacting performance, perform a parity scan during periods of low host activity.
To perform a parity scan, type:
ammgr -P
Command Example
The following example performs a parity scan on LUN 3 on disk array rack_1.
ammgr -P 3 rack_1
More About Parity Scanning
Parity information is used in RAID 5 LUNs to maintain data redundancy. When a single disk
fails in a RAID 5 LUN, the disk array can reconstruct the data on the missing disk by using
the parity information.