SERVERAID: RECOVERY PROCEDURES FOR DDD DRIVES

Subject: SERVERAID: RECOVERY PROCEDURES FOR DDD DRIVES
New Netfinity server RETAIN Tip: 

    Record number:       H026736
    Device:              D/T8680
    Model:               M
    Hit count:           UHC00000
    Success count:       USC0000
    Publication code:    PC50
    Tip key:             032
    Date created:        O99/10/25
    Date last altered:   A99/10/25
    Owning B.U.:         USA


Abstract: SERVERAID: RECOVERY PROCEDURES FOR DDD DRIVES

TEXT:

ISOLATION AIDS:

•  The system is any of the following IBM Netfinity servers:

          a Netfinity 8500R server, Type 8681, any Model.
          a Netfinity 7000-M10 server, Type 8680, any Model.
          a Netfinity 7000 server, Type 8651, any Model.
          a Netfinity 5500-M20 server, Type 8662, any Model.
          a Netfinity 5500-M10 server, Type 8661, any Model.
          a Netfinity 5500 server, Type 8660, any Model.
          a Netfinity 5000 server, Type 8659, any Model.
          a Netfinity 4000R server, Type 8652, any Model.
          a Netfinity 3500 server, Type 8644, any Model.
          a Netfinity 3500-M10 server, Type 8655, any Model.
          a Netfinity 3000 server, Type 8476, any Model.
          a Netfinity 1000 server, Type 8477, any Model.
   

•  The system is any of the following IBM PC Servers:

          a PC Server 704, Type 8650, any Model.
          a PC Server 330, Type 8640, any Model.
          a PC Server 325, Type 8639, any Model.
   

•  The system is configured with the following option(s):

   a Netfinity ServeRAID-3L Ultra2 SCSI Adapter, Option P/N 01K7364, FRU P/N 01K7352

   a Netfinity ServeRAID-3H Ultra2 SCSI Adapter, Option P/N 01K7207, FRU P/N 01K7396.
   a Netfinity ServeRAID-3HB Ultra2 SCSI Adapter, Option P/N 37L6086, FRU P/N 01K7396 (adapter), FRU P/N 09L2105 (cache).

   a Netfinity ServeRAID II

•  The system has at least one DDD drive.

DRIVE REPLACEMENT (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; however, the logical drive might contain damaged data.

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 logical 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 utility to initiate the rebuild operation, you can  unblock the blocked RAID level 0 drive when the rebuild operation completes.
•  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/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 (a defunct drive):

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

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 if "Hot-Swap" is enabled. "Hot-Swap" is enabled by default.

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.

When the ServeRAID adapter communicates with the hardfile and receives an unexpected response, the adapter will mark the drive defunct in order to avoid any potential data loss.
For example, this could occur in the event of a power loss to any of the components in the SCSI ServeRAID subsystem.
In this case, the ServeRAID adapter will err on the side of safety and will no longer write to that drive, although the drive may not be defective in any way.

For multiple DDD drives in a RAID 1 and RAID 5 array, data is lost.
Data recovery may be attempted by bringing all but the first drive that was marked DDD back to the online state.

1.  Initiate a rebuild for the first drive that was marked DDD.
    This first drive that was marked DDD has inconsistent data and must be rebuilt.
2.  Once data recovery has been attempted, a cause for the DDD drives such as a bad cable, backplane, etc. must be identified.
3.  If no cause can be found, physically replace the DDD drives one at a time so that data can be rebuilt each time.
4.  Physically replace all single DDD drives.

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