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Document ID: MCGN-44PLKD

ServeRAID - Recovery Procedures for DDD Drives

Applicable to: World-Wide

Recovery Procedures for DDD Drives

Information in this section is for use with all ServeRAID adapters listed in this HMM.

Procedures for recovering from DDD scenarios include:

The following information applies only to drives that are part of the same array

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. But remember, 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.

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:

Automatically Rebuilding the Defunct Drive
The ServeRAID adapter/controller will rebuild a defunct drive automatically when all of the following conditions exist:

Software and Physical Replacement: 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.

It is recommended to use a software replace to recover data when multiple DDD drives occur. In this situation, you may lose data on drives that are not actually defective if you run a normal rebuild process.

Perform a software replace or a physical replace according to the following criteria:

3. If the drive has been marked DDD before, physically replace the hard drive with a new one of the same capacity or greater. Proceed to step 5.
4. Proceed to step 5 to software-replace the remaining DDD drive using the ServeRAID Administration and Monitoring Utility or Netfinity ServeRAID Manager.

Refer to "Software and Physical Replacement" to understand the differences between software and physical replacement.

5. With a RAID-1 or RAID-5 logical drive, the operating system will be functional. Use either Netfinity Manager or the ServeRAID Administration and Monitoring Utility within the operating system to start the Rebuild process. With the ServeRAID Administration and Monitoring Utility, select the drive marked DDD and choose Rebuild from the menu that appears.
6. The adapter issues a start unit command to the drive. The drive then begins the Rebuild process. Once the drive completes this process, the drive's status changes to ONL.
7. If you see the message: Error in starting drive
Re-insert the cables, hard drive, and all other components to verify that there is a good connection. Go to step 5. If the error persists, go to step 8
8. Physically replace the hard drive in the DDD SID with a new one of the same capacity or greater and go to step 5
9. If the error still occurs with a known good hard drive, troubleshoot to determine if the cable, back plane, ServeRAID adapter, or other component is defective.

You can view the ServeRAID Device Event Table by selecting the logical drive from the ServeRAID Administration and Monitoring Utility. If Hard Events are reported in the ServeRAID Device Event Table, refer to "Device Event Table" for
more information. The ServeRAID adapter, in many cases, should not be replaced.

10. Once you have replaced the defective part so that there is a good connection between the adapter and the hard drive, go to step 5.
11. If software replacement brings all the drives back ONL and makes the system operational, carefully inspect all cables, etc., to ensure that the cables or backplane are not defective. Make sure that the card is seated properly. When multiple drives are marked defunct, it is often the communication channel (cable or backplane) that is the cause of the failure. If
the backplane is bowed, drives and backplane connectors may not seat properly, causing it to have a bad connection. Also, with hot-swap drives that are removed frequently, connectors could become damaged if too much force is

More Than Two DDD Drives, No RBL

The following procedure for multiple DDD drives assumes that the operating system is installed on one of the DDD drives.

1. View the ServeRAID log on another machine and write down the order in which drives went defunct.
2. Boot to the ServeRAID DOS Configuration Diskette and choose View Configuration. Make sure that the Channel Record Table contains the correct information for the status of all drives, not just those listed in the ServeRAID log.
3. Using the ServeRAID Configuration Utility program, choose Set Device State, then choose a DDD drive not listed in the
ServeRAID log to software-replace the drives. Change the state of this drive to ONL.
4. Perform the previous step until only two DDD drives are remaining. One or both of these drives should be listed as the first drive(s) to go defunct as indicated in the ServeRAID log.

If you choose the wrong order when you choose Set Device State to change the drives' states to ONL, data corruption
results. Be sure that you only change device states to ONL for drives not listed as DDD in the ServeRAID log. The first
defunct drive requires rebuilding, so it must be replaced last.

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