Re: Configuring RAID for best Oracle performance

In article <pinnacle-0501950848470001_at_hou01.onramp.net>, Pat Kelly <pinnacle_at_onramp.net> wrote:
>How should I configure a new RAID subsystem to balance the opposing
>requirements of good Oracle performance and good data availablity? I
>understand that there are trade-offs but I'd like to learn from others'
>experiences and even theories so I don't have to reinvent the wheel. It
>would be nice to have the system keep running without physical
>intervention should a disk drive fail but the users (of course!) demand
>the best performance.

If your application is write-mostly, the best configuration tip I can give you is the on/off switch if you primary goal is performance :-).

Since I did not bother to read to theories behind RAID, I find out the hard way that a RAID system is slow in writing.

>

 [ stuff omitted ]
>
>Some brainstorming we've already done: 1) mirror the transaction logs
>using two disks and put the indexes and data across the other three.
>Since all the logs together will be much less than 2 GB, this seems like a
>waste of disk. Mirroring the data using RAID 1 also may be overkill. 2)
>we could use RAID 5 across all five disks and configure three logical
>volumes: one for indexes (near the center/fastest part of the disks?), one
>for transaction logs (middle part of disk), and one for data (on the rest
>of the disks). But then there is no control over which disk drive has the
>transaction logs and indexes for (manually) optimizing performance.

Never, ever put the logs on the same subsystem as the data !!! (I assume you are using archive mode for the database, since you obviously care for your data).
And never put your archive files as the same disk as the logs or same subsystem as your data. And use 2 copies for your logs.

This gives you 3 disks besides your RAID system. The way we have it:
rootvg: 1 disk, 1 copy of the logs
uservg: 1 disk, Home of application and oracle programs, 1 copy of the logs jouvg: 1 disk, Home of all archive files raidvg: 1 RAID 7135, RAID-5 5x2 GB disk. Data and indexes.

That is the general idea (BTW, we are using raw volumes and this is screwing up LVM badly (at least we are suspecting that, there have been a lot of problems with lvrelminor, losing VGs on reboots and a lost hd5 boot volumes)). (But on the other hand, without raw volumes, oracle barely moves) (well, it moves the disk arms, but the application is not performing to good)

We also have a bigger oracle database (app 15 GB), involving RAID 7135 for data, index on 9333 mirrored to 9334 and other tricks.

/gs

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  Goran Svensson                             ! I can speak for myself, and I do
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