Re: [linux-lvm] getting pe_start right

[Mike Snitzer <snitzer@redhat.com>]

On Fri, May 06 2011 at 10:55am -0400,
Phillip Susi <psusi@cfl.rr.com> wrote:

> While trying to convert my mdadm raid5 array from metadata format
> 0.9 to 1.0, I forgot to specify the version and it defaulted to 1.2,
> which damaged the lvm metadata.  After correcting mdadm to 1.0, I
> decided to try to recreate the LVM after managing to locate the
> volume descriptions in the metadata after manually dumping it.
> 
> The problem I now have is that pvcreate will not use the same
> pe_start as before.  It was 384 and it is now 3072.  I tried using
> --metadatasize 192k --dataalignmentsize 0 and it did not help.  What
> gives?

Would be quite helpful if you shared kernel and lvm2 version info...

chances are lvm2's data_alignment_detection will shift the data start to
the start of the next full stripe of the raid5.

You should be able to specify the old start with:

--dataalignment 192k --dataalignmentoffset 0

(--dataalignmentoffset 0 likely isn't needed, but it just overrides
lvm2's data_alignment_offset detection if it just so happens that
raid5 has alignment_offset!=0)