Rebuilding a Defunct Drive

^{IBM-AUSTRIA - PC-HW-Support 30 Aug 1999}

Rebuilding a Defunct Drive

Rebuilding a Defunct Drive

When a hard disk drive goes defunct (DDD), a Rebuild operation is required to reconstruct the data for the device in its respective disk array. The ServeRAID adapters and controllers can reconstruct RAID level-1 and RAID level-5 logical drives, but they cannot reconstruct data stored in RAID level-0 logical drives.

To prevent data integrity problems, the ServeRAID adapters and controllers set the RAID level-0 logical drives to Blocked during a Rebuild operation. After the Rebuild operation completes, you can unblock the RAID level-0 logical drives, and access them once again.
But remember, the logical drive might contain damaged data.
(Refer to 'Unblocking Logical Drives' for more information.)

Before you rebuild a drive, review the following guidelines and general information.

Guidelines for the Rebuild Operation

The replacement hard disk drive must have a capacity equal to or greater than the failed drive.
If the hard disk drive being rebuilt is part of a RAID level-0 logical drive, the RAID level-0 drive is blocked.
- You must unblock any RAID level-0 logical drives at the end of the rebuild operation.
- If you use the Administration and Monitoring program to initiate the rebuild operation, you can unblock the blocked RAID level-0 drive when the rebuild operation completes.
  (See 'Unblocking Logical Drives' for more information.)
Data in a logical drive with RAID level-0 is lost during the rebuild operation. If you backed up your data before the drive failed, you can restore the data to the new drive.

General Information about the Rebuild Operation

A physical hard disk drive can enter the rebuild state if:

You physically replace a defunct drive that is part of the critical logical drive.
When you physically replace a defunct drive in a critical logical drive, the ServeRAID adapter or controller rebuilds the data on the new physical drive before it changes the logical drive state back to Okay.
The ServeRAID adapter or controller adds a hot-spare or a standby hot-spare drive to the array and changes its state from Hot-Spare or Standby Hot-Spare to Rebuilding.

Automatically Rebuilding the Defunct Drive

The ServeRAID adapter or controller will rebuild a defunct drive automatically when all of the following conditions exist:

The physical drive that failed is part of a RAID level-1 or RAID level-5 logical drive.
A hot-spare or standby hot-spare drive with a capacity equal to or greater than the capacity of the defunct drive is available the moment the drive fails.
- When multiple hot-spare drives are available, the ServeRAID adapter or controller searches for a hot-spare drive of the appropriate size. The smallest drive that meets this requirement enters the Rebuild state.
- If no hot-spare or standby hot-spare drives are available, the rebuild operation will start the moment you replace the defective drive.
NOTE: If you physically replace the drive and the new drive does not appear in the Physical Drives branch of the Main Tree, you must scan for new or removed Ready drives.
No rebuild, synchronization, or logical-drive migration operation is in process.

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