Re: ASM and disk partitions offset
Date: Thu, 16 Feb 2012 10:34:08 +0000
"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>
> > 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
> > On Feb 13, 2012, at 3:13 PM, "Radoulov, Dimitre" <cichomitiko_at_gmail.com>
> >> 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
> >> [...]
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- Niall Litchfield Oracle DBA http://www.orawin.info -- http://www.freelists.org/webpage/oracle-lReceived on Thu Feb 16 2012 - 04:34:08 CST