Re: AIX/ORACLE - Raid devices - async I/O [SUMMARY]

In article <Cz9Mto.7wH_at_world.std.com>, Lee E Parsons <lparsons_at_world.std.com> wrote:
>These were the responses I got to the following question.
>
>> We are using AIX 3.2.5 and Oracle 7.0.16. We are currently looking at the
>> I/O configuration and I had a couple of questions.
 

>> 1) The Unix Gang wants to take our raid subsystem and create one filesystem
>> across all five drives in the array replacing the 5 filesystems we have
>> now. The only thing on this array is oracle datafiles so it sounds like
>> a reasonable plan. Instead of having 5 FS's that are striped across
>> 5 disks we'll have 1 FS across the same disks.
>>
>> All things being equal, can anybody think of a good reason not to do this?

Assuming you are talking about Raid Level 5, it may or it may not be a good idea. We have here a 10+ GB oracle database, running on a mix of 9334/9333 subsystems and a IBM Raid 7135. And we also have a 4 GB database trying to run on a 5x2GB 7135 Raid.

First, if you are not running raw devices, do so. Raw devices will give you a performance boost (assuming you have more then 10 users) (but also a lot of headache when it comes to backups). (And start archiving if you have not done so already).

Second, the 7135 is very good if you have many users doing reads, he is 50% faster then a single 9333 serial disk and performance is best when there are a lot of users. If you start to mix it with writes, performance will drop. For our database, we have the data tablespace stored on the Raid, and the index tables space on 9333 Serial disks mirrord to 9334 1.2/2.4 GB SCSI-2 disks for optimum read performance.

Third, if you have your entire database on a Raid-5, you will see bad performance when it comes to indexing and dtabase updates (at least on the 7135, a hardware write cache may help you out). You may alse take a look at the IBM database accelerator which does some hardware magic for oracle and other databases. Unfortunately it does not support 9333 or Raid.

[snip]

> It should be a big win for you to have a much bigger file system space.

Note the 2 GB filesystem limit.

>
>

/gs

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