Re: Subject: RE: ASM - number of LUNS rule of thumb

From: David Robillard <>
Date: Fri, 13 Aug 2010 10:32:20 -0400
Message-ID: <>

Hello Andrew,

> Is that true if you are using external redundancy?

Yes. You need LUNs of equal size for all types of redundancy with ASM.

When you use either high or normal redundancy, what you do is simply activate the mirroring capbability of ASM. While if you use external redundancy, you don't use it. But in all three types of redundancy, ASM prefers LUNs of equal sizes.

Note that you're not forced to use LUNs of equal sizes. ASM will not complain. But performance will suffer and you might end up wasting disk space.

So in the end, you're better off using LUNs of equal sizes ;)


> On Fri, Aug 13, 2010 at 7:49 AM, David Robillard <> wrote:

>> Hello George,
>> One thing to keep in mind with ASM is that all LUNs in your disk
>> groups must be of equal size.
>> So if you use, say, 100 GB LUNs with ASM. Then when your database
>> needs more storage, you'll need to add a 100 GB LUN to your disk
>> group.
>> There was an interesting presentation on ASM on
>> Do a search for %ASM% in the documents
>> section of the site.
>> HTH,
>> David
Received on Fri Aug 13 2010 - 09:32:20 CDT

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