Re: What would you do with 8 disks?

Only one guy mentioned ASM, nobody asked whether it's hardware or software RAID... or what operating system you're using (for software RAID)... As Niall pointed out, there is indeed no correct answer without first soliciting more data - particularly about your requirements. We're deploying systems with local disk in several of the suggested configurations and we tend to favor either hardware RAID or ASM for data protection. I don't think that we still micromanage file-to-spindle mappings for any of our databases... it's very tedious and IMHO the small benefit isn't worth the large effort. Especially when you have a few DBA's managing a lot of databases.

If you have time and it's hardware RAID, I'd suggest setting up both a RAID5 glob of all the disks and subsequently a RAID10 configuration on the same box, and running orion on both (make sure to run it long enough to exhaust any cache effect). Then you have some precise numbers and you can see exactly what the performance/space trade-off will be.

If you're deploying a large number of boxes in a "standard" configuration (as we do), then you also might be working with vague requirements - "what do I think will be best for the most people over the next months/years"... and that's a horse of whole different color. :) I had a conversation just a few days ago about nearly this exact question. Our platform guys always reserve two disks for the OS, and we're probably going to recommend a single hardware RAID5 glob of everything else for the oracle-related stuff... if only because it's simple to support and 8 local disks is a small configuration for us... so people will probably not be ordering this particular config if they need high performance. But it hasn't quite been nailed down yet.

-Jeremy

Niall Litchfield wrote:
> Well I can't quite believe that no-one has asked what the capacity
> requirements are and the capacity that your server will hold, what the
> recovery time requirements are, the disk controller config, the
> capacity plan for the db, how many iops you need and so on. Still in
> the absence of any of that, i'm quite happy to agree that raid 10/01
> is nicer than raid 5, more economical per io, less economical per mb.
> I'm also happy to agree that manual striping is much more fun than
> letting the hardware and software do it and can sometimes be nearly as
> good! Me, i'd try and get answers to the first set of questions and
> see if we couldn't use technology such as the raid controllers and asm
> to deal with the micromanagement of the second.
>
> On 4/8/09, Mir M. Mirhashimali <mhyder_at_rice.edu> wrote:
>
>> I kinda like to spread my redo to several disks
>>
>> I have 4 disks and i write the redo logs as follows
>>
>> Disk1 - OS
>> G01_M1 on disk2
>> G01_M2 on disk3
>> G02_M1 on disk3
>> G02_M2 on disk4
>> G03_M1 on disk4
>> G03_M2 on disk2
>>
>> and so on
>>
>> this way redo is safe from disk failure.
>>
>>
>> -original message-
>> Subject: What would you do with 8 disks?
>> From: "dave" <david.best_at_gmail.com>
>> Date: 08-04-2009 07:49
>>
>> Hey all,
>>
>> If you had 8 disks in a server what would you do? From watching this
>> list I can see alot of people using RAID 5 but i'm wary of the
>> performance implicatons. (http://www.miracleas.com/BAARF/)
>>
>> I was thinking maybe RAID 5 (3 disks) for the OS, software and
>> backups. RAID 10 (4 disks + 1 hot spare) for the database files.
>>
>> Any thoughts?

-- 
Jeremy Schneider
Chicago, IL
http://www.ardentperf.com

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