HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 - (English) Advanc - Page 306
Performing a Parity Scan, amount, Command Example, amutil -R 4 -f 5 -a 16 05EBD20
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• amount identifies the number of blocks to rebuild at a time. This value can be from 1 to 64K 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 Kbytes 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. 306 Managing the Disk Array Using Array Manager 60