[linux-lvm] logical volumes and raid alignment

[Luca Berra]

On Sun, May 02, 2010 at 10:33:03PM +0200, Alexander 'Leo' Bergolth wrote:
>Hi!
>
>I am using LVM on a hardware RAID 5 and I'd like to tune the alignment
>of lvm extents to match the raid stripe size.
>
>My raid chunk size is 64k and I am using 5 data-bearing discs (raid 5
>with 6 discs), so the raid stripe size should be 64k * 5 = 320k.
>
>I have already managed to properly align the partition to a multiple of
>this value and I am able to align the beginning of the first extent by
>specifying --dataalignment 320k to pvcreate.
>
>But unfortunately the --physicalextentsize must be a power of 2, so I
>cannot use a multiple of 320k as the physical extent size.
>
>What are your experiences with tuning and properly aligning lvm + raid?
>Does anyone know a workaround?
I had a similar issue, and best thing i came up with was creating volume
group with PE Size == chunk_size, and create/extend all logical volumes
to a multiple of data_disks PE.

L.

-- 
Luca Berra -- bluca at comedia.it
         Communication Media & Services S.r.l.
  /"\
  \ /     ASCII RIBBON CAMPAIGN
   X        AGAINST HTML MAIL
  / \