I know we've been over this, but times change, and technology changes. Conventional Wisdom on this list has been that the best disk layout for your TSM Database is:
JBOD disks, Raw volumes, mirrored by TSM, with 2 dbvols per physical volume. (This is what I am using now.) I've got all the databse people I talk to here saying I'm crazy. They say to use RAID, with lots of striping, and mirrored in hardware. Example: IBM Redbook SG24-5511-01 "Database Performance Tuning on AIX". Example 2: Oracle documentation. (At least I have talked them out of RAID5, which we know to be a dog on writes, since client node backups (lots of writes) are the worst database performance issue we have.) After I disabused them of RAID5, they say: Hardware RAID10, raw volumes, and no advice about dbvol size. Has anybody actually tried both and can comment on the comparison? I'm at the point where I need to enlarge my database anyway, and it's not performing as well as I'd like, so I figure this is a good time to change its layout. I'm thinking of: Hardware 2x2 SSA RAID10 (2-way striped mirrored pairs), raw volumes, 4 dbvols per virtual RAID volume (hdisk), which is still 2 dbvols per real disk. There has been some discussion of relative database corruption risk with TSM mirroring versus hardware or OS mirroring. Some say that TSM mirroring gives you greater protection against software-caused corrution. I don't get it, as long as MIRRORWRITEDB is set to Parallel. Unless I'm missing something, TSM MIRRORWRITEDB PARALLEL should have the exact same risk level as hardware/OS mirroring. Has anybody actually had their skin saved by TSM mirroring, as opposed to hardware/OS mirroring, or is this greater protection just hypothetical? Roger Deschner University of Illinois at Chicago [EMAIL PROTECTED]
