Phillip raises a valid point, which I can reinforce. We also have configured our TSM DB and LOG volumes on IBM FAStT (900s), using RAID5 LUNs. We mirror pairs of them using TSM mirroring. We recently had a convoluted situation that caused our server to crash, and it would not come up due to a corrupted log. We were able to bring up the server in "verify" mode and it was able to recover the log using the mirror copies.
Details: We have a rack which contains our TSM AIX server along with a CISCO SAN Director. The rack has 4 power circuits. All equipment had dual power supplies, however - due to a human oversight - two of the RIO drawers had their redundant power supplies plugged into the same circuit. I know - a preventable error, but nonetheless, this resulted in log corruption that would have caused us much more grief had we not had the mirror copy. A power supply in the SAN Director blew, tripping the circuit that also had both redundant power supplies in the RIO drawer, taking down our AIX server hard. ..Paul At 02:30 PM 1/20/2006, Ford, Phillip wrote:
I believe there is still a reason to mirror at the TSM level. If you mirror at the hardware level only and TSM writes a corrupt entry to the DB or log, you are hosed since the hardware mirror will write it to both copies. If TSM is doing the mirror, it can see that it had a problem writing to one copy and not write the corrupt data to the second copy. TSM can then use the good copy to fix the corrupt mirror. Now I do not know how or when this case can come up but that is the reason I was told to mirror at the TSM level. We use EMC for the storage. All our EMC storage is mirrored or raided. We then also mirror at the TSM level. This is over kill but we do not have any unprotected disks to use so we double do it. Have not had a problem but we may be wasting disks. -- Phillip 320-4462
-- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Systems Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [EMAIL PROTECTED]
