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IBM-AUSTRIA - PC-HW-Support 30 Aug 1999 |
RAID Recovery Procedure Not Effective
RAID Recovery Procedure Not Effective
Symptom:
A single drive failed, but 2 RAID fixed disk drives appear as DDD
(Defunct the drive is not responding to commands). Routine recovery procedures
are ineffective in bringing the DDD drive(s) back on-line.
NOTE: The system may have run without problems for some time.
Problem Isolation AIDs
- The system is a Server 500 RAID Array (8641)
- The system diagnostics do not fail
- The RAID Administration program appears normal
- More than one DASD backplane is installed
Fix: / Background
The RAID controller requires two cables to be attached to the DASD backplane in order to maintain control of the
RAID subsystem, the SCSI signal cable (wide), and a much smaller Status cable.
The backplane in Bank C must be attached to SCSI Connector Channel 1.
If installed, DASD backplane in Bank D would be attached to SCSI Connector Channel 2. The same is true of the Status cables.
Status connector 1 must be attached to DASD backplane C and Status Connector 2 must be attached to DASD backplane D, if installed.
The signal cable and status cables for each channel may not be connected to the same backplane. (For example: The Status cable for the backplane is
mistakenly connected to bank D, and vice-versa). In this case, the RAID adapter is not communicating with the correct backplane (but has no way of knowing this), so
erroneous status information is being presented to the RAID adapter.
Attempting to rebuild a fixed disk with the cables connected in this manner will probably result in customer data loss.
In systems which have more than one DASD backplane installed, make certain that the RAID Channel 1 (SCSI) signal cable and the RAID Channel 1 Status cable are both attached
to the same backplane (are not crossed).
See > RAID Cabling / Samples
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