Re: RAID 1 or RAID 10?

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Wed, 22 Dec 2004 14:14:12 +1100
Message-ID: <41c8e68b$0$1119$afc38c87@news.optusnet.com.au>

DA Morgan wrote:

> Ric wrote:
> 

>> Just about to set up our new Oracle server. The box is a Dell
>> PowerEdge 2850, Dual Xeon 3.6GHz with 4 Gb RAM and 4x 18Gb 15,000 RPM
>> Drives. I am about to set up the RAID array and am unsure as what
>> would be best. I was originally going to use RAID 5 but am unsure now
>> as I have read so many bad things about using it with Oracle. Some
>> form of redundancy is requred so here are my proposed alternatives:
>>
>> 1) 2x RAID 1 arrays - this would give me a total of 36Gb and as each
>> volume would be mirrored I would have the necessary fault tolerance.
>> I could then split data across the two arrays, i.e. Windows Server
>> 2003 and system files on one and data files on the other
>>
>> 2) 1x RAID 10 array - this would have the data striped over two disks
>> which would be mirrored to provide the fault tolerance. I would only
>> have one volume but there would be a performance increase due to the
>> striping. I'm not sure if there is much worth to having a stripe set
>> with only two disks.
>>
>> Any strong feelings or opinions?
>>
>> Thanks.

> 
> 
> I second your concerns. I see no value in RAID 5 

Hold that thought...

> and would make the
> decision of (1) or (2) based on a realistic appraisal of when you will
> be able to purchase additional disks which, quite frankly, would be my
> choice. 

...and this one.

Now put the two together. Assume, just for the moment, that you have no more money; that all hard disk manufacturers have gone out of business; that the world's entire stock of hard disks on retailer's shelves has disappeared. He's got four disks, in other words, and four disks is all he's going to have.

Still see no value in RAID 5?

It is fine to express concerns, and it is finer to advocate more disks. But it is a little reckless to declare "no value" in something which would actually provide striping and redundancy with the number of disks he already has.

You propose instead two mirrored sets and no striping at all. And this for a database which, without mirroring, but with archivelog, is ordinarily never going to lose committed data (ie, it has a measure of redundancy already built in). Don't you think that's a little BAARF-purist of you? Given that one could always perform a database recovery if in archivelog mode, why not RAID-0 it and have done?

> After purchasing Oracle and the hardware ... why not get some
> additional disks given the low cost.
> 
> Presumably you will want some room for archived log files, etc.

What can we conclude from your post? That four disks is really insufficient to run Oracle?

But which proportion of the world's installed Oracle base would you care to guess uses 4 disks or fewer?

Your Boeing background is showing again Daniel: Not all the world is in that class. And you need to come up with practical advice for the huge chunk of it that isn't. And RAID 5 should be in that armoury of advice.

HJR Received on Tue Dec 21 2004 - 21:14:12 CST