Re: ASM Question - Best Practice

From: Palooka <>
Date: Wed, 04 Jun 2008 19:49:56 +0100
Message-ID: <ptB1k.82456$x55.67542@newsfe17.ams2>

K Gopalakrishnan wrote:
> Palooka,
> Good that you are asking the questions at planning phase (!),

>> The intention is to use ASM. So first question: The mirroring can be
>> done within ASM; i.e. by Oracle, or we can do it at the SAN level.
>> Any advice or recommendations as to which is likely to be better?
>> Availability and resilience will probably rank ahead of performance in
>> terms of user requirements.

> The choice is totally yours. If you think your SAN mirroring is better
> than ASM you can use SAN mirroring and choose the external redundancy
> to ASM. In short, ASM mirroring is done at the 'server' level and SAN
> mirroring is done at 'controller' level. So there may be some
> additional CPU overheads in ASM mirroring which may or may not be an
> issue.
> However with ASM mirroring, you have the luxury of having many disk
> groups with different redundancy levels, like double or triple
> mirroring for system/data and no mirroring for temp tablespaces and so
> on. You can do the same at SAN level, but that is not as simple as you
> do in ASM.
> Also you don't need to reserve a hot spare for ASM mirroring as ASM
> mirrors the 'extents' which are just 1M pieces of storage blocks (aka
> allocation units). This gives a better utilization of available disks,
> but doesn't matter these days!!

Thanks Gopal, and to all others who responded. It'll be interesting to see what Frank has to say about the "bug pit". I hope he will amplify.

Palooka Received on Wed Jun 04 2008 - 13:49:56 CDT

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