HP 226593-B21 Smart Array 5i Plus Controller and Battery Backed Write Cache En - Page 100

Drive Failure During Rebuild, Minimizing Fatal System Errors During Rebuild

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Hard Drive Installation and Replacement • When you set the SCSI ID jumpers manually, check the ID value to be sure that the correct physical drive is being replaced. Set the same ID value on the replacement drive to prevent SCSI ID conflicts. CAUTION: In systems using external data storage, take care that the server is the first unit to be powered down and the last to be powered back up. Doing this ensures that the system will not erroneously mark the drives as failed. The rebuild operation takes several hours, even if the system is not busy while the rebuild is in progress. System performance and fault tolerance are both affected until the rebuild has finished. Therefore, replace drives during low activity periods whenever possible. In addition, be sure that all logical volumes on the same array as the drive being replaced have a current, valid backup. Drive Failure During Rebuild If another drive in the array fails while fault tolerance is unavailable during rebuild, a fatal system error may occur. If this happens, all data on the array is lost. In exceptional cases, however, failure of another drive need not lead to a fatal system error. These exceptions include: • Failure after activation of a spare drive • Failure of a drive that is not mirrored to any other failed drives (in a RAID 1+0 configuration) • Failure of a second drive in a RAID ADG configuration Minimizing Fatal System Errors During Rebuild When a hard drive is replaced, the controller gathers fault-tolerance data from the remaining drives in the array. This data is then used to rebuild the missing data (originally on the failed drive) onto the replacement drive. If more than one drive is removed at a time, the fault-tolerance data is incomplete. The missing data cannot then be reconstructed and is likely to be permanently lost. D-8 Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache User Guide

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Hard Drive Installation and Replacement
D-8
Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache User Guide
•
When you set the SCSI ID jumpers manually, check the ID value to be sure that
the correct physical drive is being replaced. Set the same ID value on the
replacement drive to prevent SCSI ID conflicts.
CAUTION:
In systems using external data storage, take care that the server is the
first unit to be powered down and the last to be powered back up. Doing this ensures
that the system will not erroneously mark the drives as failed.
The rebuild operation takes several hours, even if the system is not busy while the
rebuild is in progress. System performance and fault tolerance are both affected until
the rebuild has finished. Therefore, replace drives during low activity periods
whenever possible. In addition, be sure that all logical volumes on the same array as
the drive being replaced have a current, valid backup.
Drive Failure During Rebuild
If another drive in the array fails while fault tolerance is unavailable during rebuild, a
fatal system error may occur. If this happens, all data on the array is lost. In
exceptional cases, however, failure of another drive need not lead to a fatal system
error. These exceptions include:
•
Failure after activation of a spare drive
•
Failure of a drive that is not mirrored to any other failed drives (in a RAID 1+0
configuration)
•
Failure of a second drive in a RAID ADG configuration
Minimizing Fatal System Errors During Rebuild
When a hard drive is replaced, the controller gathers fault-tolerance data from the
remaining drives in the array. This data is then used to rebuild the missing data
(originally on the failed drive) onto the replacement drive. If more than one drive is
removed at a time, the fault-tolerance data is incomplete. The missing data cannot
then be reconstructed and is likely to be permanently lost.