I moved our large AIX ITSM 5.1 server to Raw Logical Volumes without suffering any loss of performance. Migration still runs at about the rated speed of the S-DLT tape drives. The database is, if anything, slightly faster. With RLVs, the application (ITSM) is closer to the hardware, so there is less to protect you against mistakes in your I/O configuration. Not anything esoteric, just good Best Practices in I/O confiuguration management. Spread the load out among as many disk heads and I/O channels as possible, and watch out for bottlenecks.
One gotcha in this regard is if the volumes in a diskpool are radically different sizes, watch out for an I/O bottleneck on the larger volumes as the pool fills up. That's because the smaller volumes will fill completely, shifting the active I/O load entirely to the larger volumes. Circumvent this by combining smaller PVs into larger RLVs (using striping of course) that will more or less match your larger PVs. You do not need to match the sizes exactly. The IBM manuals warn you repeatedly about the dangers of Raw Logical Volumes. If you enlarge one, the TSM data within it is destroyed. This danger can be partially avoided by setting the Max LPs to the same as the current LPs. That way at least there's a safety latch on the gun pointed at my foot - I would have to change two things. This thread started with slow performance of dsmfmt, and that is where the greatest performance advantage of RLVs is - you don't run dsmfmt at all! Even if RLVs were slightly slower, which I do not believe is true if you put a little management effort into it, I'd still use them because of the amount of MY time they save. Roger Deschner University of Illinois at Chicago [EMAIL PROTECTED] On Sat, 21 Feb 2004, Paul Ripke wrote: >On Friday, Feb 20, 2004, at 09:16 Australia/Sydney, Justin Bleistein >wrote: > >> according to the aix tsm server performance manual it states that it >> rlv's >> may buy you performance in client backup and restore operations but >> not in >> server data movement operations such as migration. > >OK, I haven't touched TSM on AIX for 4 or so years, but when I migrated >our two Sun TSM servers from ufs to raw VxVM volumes, I didn't notice >any degradation in any aspect of TSM operations. I'm somewhat surprised >that there would be a degradation of performance for operations like >migrations using raw LVs on AIX... > >Cheers, >-- >Paul Ripke >Unix/OpenVMS/TSM/DBA >I love deadlines. I like the whooshing sound they make as they fly by. >-- Douglas Adams >
