Re: ASM and disk partitions offset

From: Niall Litchfield <niall.litchfield_at_gmail.com>
Date: Thu, 16 Feb 2012 10:34:08 +0000
Message-ID: <CABe10sbniaqKEmPKQ9Yt2VcSkZmo6xFezpX_8cb7X6RDhx9Ekw_at_mail.gmail.com>

Dimitre,
"I wouldn't bother" is probably incorrect. The details will depend on the array stripe size, the sector sizes and probably the specific hardware. That said most vendors recommend the 1mb starting point for a partition because it has as a common divisor most of the usual allocation unit sizes and disk label sizes. I quite like this article http://blogs.msdn.com/b/jimmymay/archive/2009/05/08/disk-partition-alignment-sector-alignment-make-the-case-with-this-template.aspx written from a windows perspective with SQL in mind, but really the basic issue isn't software specific. FWIW Oracle, Microsoft and VMWare all recommend that you align your storage hardware with the FS/Volume manager so as to avoid doing multiple IO requests where a single request would do, references below.

http://www.vmware.com/pdf/Perf_Best_Practices_vSphere4.0.pdf
http://www.oracle.com/technetwork/articles/systems-hardware-architecture/lun-alignment-163801.pdf
http://support.microsoft.com/kb/929491

On Thu, Feb 16, 2012 at 10:12 AM, Radoulov, Dimitre <cichomitiko_at_gmail.com>wrote:

> On Thu, Feb 16, 2012 at 7:29 AM, Stalin Subbiah <stalinsk_at_gmail.com>
> wrote:
> > I believe it was also done to align ASM disks with stripe size which is
> generally in multiples of 2. At least this was the case with Linux, using
> fdisk for disk partitions.
>
> Thanks Stalin,
> but what that means: that a partition beginning at the first cylinder
> is not aligned with the HW stripe size (presumably a power of 2)?
>
> I've asked if the storage team had some special requirement (or
> suggestion) as far as the first cylinder of the partitions is
> concerned and I've received a generic reply that I shouldn't bother.
>
>
> Best regards
> Dimitre
>
>
> > On Feb 13, 2012, at 3:13 PM, "Radoulov, Dimitre" <cichomitiko_at_gmail.com>
> wrote:
> >
> >> I meant:
> >>
> >> now I remember that once, when I was setting up a test RAC on Solaris, I
> >> wasn't able to make the partitions visible for asm disk creation
> >> [...]
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

-- 
Niall Litchfield
Oracle DBA
http://www.orawin.info


--
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Received on Thu Feb 16 2012 - 04:34:08 CST