[Ocfs2-users] partition offset/alignment on SAN devices.

[James Masson]

On 09/07/10 12:35, Luis Freitas wrote:
> Thomas and James,
>  
>    Usually the partition is aligned to the Cylinder boundary. In the
> case of a LUN, the cylinder bondary might have no sense at all? Funny, I
> never tought about this before.
>  

In the old days C/H/S geometry used to be relevant, and fdisk used this information when
partitioning. Now it's pretty much irrelvant, and since exported LUNs don't present this data, fdisk
uses a default that's pretty hostile to performance.

It's not a huge issue with OCFS2 data, because you can always manually change the alignment
afterwards. With virtual machines and kick-starts, it's very relevant, as it's awkward to change the
partition layout of a VM after the fact.

I've had this raised as a bug through an enterprise support contract with Redhat for at least a
year. Microsoft have had sane defaults (1Mb offset for partition table) for a while now.

James M

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