Re: DASD Disk Layout Advice

From: Pat <pat.casey_at_service-now.com>
Date: Fri, 27 Nov 2009 07:45:39 -0800 (PST)
Message-ID: <9373db60-113a-4c5c-aba1-ce0c8bb23eea_at_e4g2000prn.googlegroups.com>

Thanks for the feedback guys, that's exactly what I was looking for.

Oracle 10.2.0.4, OS is Red-Hat ES 5 (64 bit). Controller does support multiple paths, and we'll be running the database with asynchronous IO enabled (although I'm not thinking that'll impact disk layout, but I've been wrong before).

A couple of comments (in no particular order) based on some questions folks asked:

1. Somebody mentioned aligning the multiblock read count with the raid stripe size ... we've gotten in the habit with 10.2 of unsetting db_file_multiblock_read_count and just letting Oracle set it based on how it observers the IO subsystem behaving. So far, that's seemed to worked out pretty well for us, since my experience is not everybody gets it right if they have to hand tune it.
2. App isn't all that commit happy. It generates a fair amount of redo, but it tends to commit reasoanbly large transactions at once so the number of commits doesn't usually saturate the IO subsystem, at least it doesn't on my netapp installations and they have much larger transaction volume than I'm expecting to see here.
3. RAID 5 ... with todays' controllers is that getting used more often? It was drilled into my head years ago that you don't put OLTP data on RAID 5, but then it was drilled into my head that you never mount your tablespace over NFS too and that changed :)

In any event it sounds like now that pretty much everyone's agreed that splitting "index" from "data" on a config like this is probably counterproductive. The main open questions are just how to lay out redo on whether or not RAID5 is an option. Received on Fri Nov 27 2009 - 09:45:39 CST