HP Smart Array 6400 Series Controller Support Guide

If the Online LED of the replacement disk drive stops blinking during automatic data recovery, there are three possible causes:

• If the Online LED is glowing continuously, automatic data recovery is successful and finished.

• If the Fault LED is illuminated or other LEDs go out, the replacement disk has failed and is producing unrecoverable disk errors. Remove and replace the failed replacement disk.

• If the automatic data recovery process has abnormally terminated, one possible cause is a noncorrectable read error on another physical disk. Locate the faulty disk, replace it, and restore data from backup.

Physical Disk Replacement Overview

CAUTION: A disk that was previously failed by the controller can seem to be operational after the system is power-cycled, or (for a hot-pluggable drive) after the drive has been removed and reinserted. However, continued use of such marginal drives can result in data loss. Replace all marginal drives as soon as possible.

Consider these factors when replacing a disk:

• Non-hot-pluggable drives can only be replaced while the system is powered off.

• Hot-pluggable disks can be removed and replaced at any time.

• When a hot-pluggable disk is inserted, all disk activity on the array pauses while the new drive is spinning up (usually 20 seconds). If the disk is inserted when power is on in a fault-tolerant configuration, data recovery onto the replacement drive begins automatically, indicated by the blinking Online LED.

• Replacement disks must have a capacity no less than that of the smallest disk in the array.

Disks with insufficient capacity are failed immediately by the controller, before automatic data recovery begins.

IMPORTANT:

In systems using external data storage, be sure that the server is the first unit to be powered off and the last to be powered back on. 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 disks during low activity periods whenever possible. In addition, be sure that all logical drives on the same array as the disk being replaced, have a current, valid backup.

Physical Disk Failure During Rebuild

If another disk in the array fails when fault tolerance is unavailable during rebuild, a fatal system error can occur. If this happens, all data on the array is lost. In exceptional cases, however, failure of another disk does not lead to a fatal system error. These exceptions include:

• Failure after activation of a spare disk

• Failure of a disk that is not mirrored to any other failed disk (in a RAID 1+0 configuration)

• Failure of a second disk in a RAID ADG configuration

Minimizing Fatal System Errors During Rebuild

When a physical disk is replaced, the controller gathers fault tolerance data from the remaining disks in the array. This data is then used to rebuild the missing data from the failed disk onto the replacement disk. If more than one disk 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.

Physical Disk Replacement Overview 71

To minimize the likelihood of fatal system errors, take the following precautions when removing failed disks:

• Do not remove a degraded drive when any other disk in the array is offline (the Online LED is off). The following exceptions apply:

• When RAID 1+0 is used, drives are mirrored in pairs. Several disks can fail simultaneously, and they can all be replaced simultaneously without data loss as long as no two failed disks belong to the same mirrored pair.

• When RAID ADG is used, two disks can fail simultaneously and be replaced simultaneously without data loss.

• If an online spare has an unlit Online LED (is offline), it can still be replaced.

• Do not remove a second disk from an array until the first failed or missing disk has been replaced and the rebuild process is complete. When the rebuild is complete, the Online LED on the front of the disk stops blinking and glows steadily. The following exceptions apply:

• In RAID ADG configurations, any two disks in the array can be replaced simultaneously.

• In RAID 1+0 configurations, any disks that are not mirrored to other removed or failed disks can be simultaneously replaced offline without data loss.

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