Compaq ProLiant 8000 ProLiant 8000 Servers Maintenance and Service Guide - Page 36

Hot-Plug Drive Replacement Guidelines, Unsafe Hot-Plug Drive Replacement Precautions, CAUTION

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Removal and Replacement Procedures 2-19 Hot-Plug Drive Replacement Guidelines You should be able to hot-plug a drive during normal activity. Be aware, however, that hot-plugging a disk drive will effect system performance and fault tolerance. NOTE: Depending upon your configuration, both a drive failure and the subsequent rebuild process will cause storage subsystem performance degradation. For example, the replacement of a single drive on an array with 50 logical drives will have less impact than if the array has three logical drives. When a disk drive is hot-plugged, although the system is functionally operational, the disk subsystem may no longer be fault tolerant. CAUTION: Fault tolerance will be lost until the removed drive is subsequently replaced and the rebuild operation is completed (this will take several hours, even if the system is not busy while the rebuild is in progress). If another drive in the array should incur an error during the period when fault tolerance is unavailable, it is possible to cause a fatal system error due to a data error. If another drive fails during this period, the entire contents of the array will be lost. IMPORTANT: It is recommended that disk drive replacement be performed during low activity periods whenever possible. In addition, a current valid backup should be available for the logical drives in the array of the drive being replaced, even if drive replacement is being made during server downtime. Unsafe Hot-Plug Drive Replacement Precautions Be aware of the following Compaq guidelines cautioning unsafe hot-plug replacement. Do not remove a degraded drive if any other member of the array is off-line (the online LED is off). No other drive in the array can be hot-plugged without data loss. The possible exception to this might be the utilization of RAID 0+1 as a fault tolerant form. In this case, drives are mirrored in pairs. More than one drive can fail and be replaced as long as the drive or drives they are mirroring are online. Refer to your Smart Array Controller user guide for information on fault tolerance options. Do not remove a degraded drive if any member of an array is missing (previously removed and not yet replaced). Do not remove a degraded drive if any member of an array is being rebuilt, unless the drive being rebuilt has been configured as an online spare. The online LED for the drive will be flashing, indicating that a replaced drive is being rebuilt from data stored on the other drives. NOTE: An online spare will not activate and start rebuilding after a predictive failure alert, because the degraded drive is still online. The online spare activates only after a drive in the array has failed. Do not replace multiple degraded drives at the same time (for example, when the system is off), since the fault tolerance may be compromised. When a drive is replaced, the controller uses data from the other drives in the array to reconstruct data on the replacement drive. If more than one drive is removed, a complete data set is not available to reconstruct data on the replacement drive or drives and permanent data loss could occur.

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Removal and Replacement Procedures
2-19
Hot-Plug Drive Replacement Guidelines
You should be able to hot-plug a drive during normal activity. Be aware, however, that
hot-plugging a disk drive will effect system performance and fault tolerance.
NOTE:
Depending upon your configuration, both a drive failure and the subsequent rebuild process will
cause storage subsystem performance degradation. For example, the replacement of a single drive on an
array with 50 logical drives will have less impact than if the array has three logical drives.
When a disk drive is hot-plugged, although the system is functionally operational, the disk
subsystem may no longer be fault tolerant.
CAUTION:
Fault tolerance will be lost until the removed drive is subsequently replaced and the
rebuild operation is completed (this will take several hours, even if the system is not busy while
the rebuild is in progress). If another drive in the array should incur an error during the period
when fault tolerance is unavailable, it is possible to cause a fatal system error due to a data
error. If another drive fails during this period, the entire contents of the array will be lost.
IMPORTANT:
It is recommended that disk drive replacement be performed during low activity periods
whenever possible. In addition, a current valid backup should be available for the logical drives in the
array of the drive being replaced, even if drive replacement is being made during server downtime.
Unsafe Hot-Plug Drive Replacement Precautions
Be aware of the following Compaq guidelines cautioning unsafe hot-plug replacement.
■
Do not remove a degraded drive if any other member of the array is off-line (the online
LED is off). No other drive in the array can be hot-plugged without data loss. The possible
exception to this might be the utilization of RAID 0+1 as a fault tolerant form. In this
case, drives are mirrored in pairs. More than one drive can fail and be replaced as long as
the drive or drives they are mirroring are online.
Refer to your Smart Array Controller user guide for information on fault tolerance
options.
■
Do not remove a degraded drive if any member of an array is missing (previously
removed and not yet replaced).
■
Do not remove a degraded drive if any member of an array is being rebuilt, unless the
drive being rebuilt has been configured as an online spare. The online LED for the drive
will be flashing, indicating that a replaced drive is being rebuilt from data stored on the
other drives.
NOTE:
An online spare will not activate and start rebuilding after a predictive failure alert, because the
degraded drive is still online. The online spare activates only after a drive in the array has failed.
■
Do not replace multiple degraded drives at the same time (for example, when the system is
off), since the fault tolerance may be compromised. When a drive is replaced, the
controller uses data from the other drives in the array to reconstruct data on the
replacement drive. If more than one drive is removed, a complete data set is not available
to reconstruct data on the replacement drive or drives and permanent data loss could
occur.