Re: ASM stripe width in 10g

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Hi Kevin

"Kevin" <kevin_rm_at_pimmentos.com> wrote in message news:ac0288a2.0408041211.750fb0f1_at_posting.google.com...
> Will the real stripe width in ASM please step forward?
>
> I've been reading conflicting views on the stripe width for ASM
> recently. Someone please set me straight on this.
>
> First, I heard that ASM performs its striping at the extent level. In
> this case, all the extents would be spread out over all the disks in
> the disk group.

Can you provide a link?

> I've also read that ASM stripes the data according to the template
> setup for the specific data file (v$asm_template). Inside the
> template, you can specify only one of two stripe sizes, coarse or
> fine. Coarse being 1MB, fine being 128k. It seems that this would be
> the way to go. In this case your stripes would be one of these sizes
> regardless of your extent size.

This information is reported many times in the Oracle documentation, therefore, in my opinion, is correct. Anyway I never had the time to check it...

> Additionally, ASM claims to prevent fragmentation. I don't buy this
> either. If fragmentation refers to the sizeable space unavailable in
> a datafile because no objects can allocate their next extent inside
> it, and I can still have a dictionary managed tablespace using ASM, I
> could still find a way to get some very fragmented data files.

In my opinion ASM prevents fragmentation just like locally managed tablespaces with uniform allocation do.
When used with dictionary managed tablespaces I guess that over allocation of space will be performed. Unfortunately I never tested this point because 1) it makes no sense to use dictionary managed tablespaces 2) all my 10g databases have a locally managed SYSTEM tablespace

Chris

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