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Re: [linux-lvm] logical volumes and raid alignment

On Sun, May 02, 2010 at 10:33:03PM +0200, Alexander 'Leo' Bergolth wrote:

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.


Luca Berra -- bluca comedia it
        Communication Media & Services S.r.l.
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