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Storage system: HP Smart Array P410i. Operating system: RHEL 5.5 x86_64.

I have created a RAID 1+0 logical drive consisting of 12 disks, stripe size 128KB. With this logical drive, I'm about to create a new LVM volume group. Now, what physicalextentsize should I choose?

Troels Arvin
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Performance-wise that should not matter very much. Back in the LVM1 days a small PE size severely limited the maximum volume size, with LVM2 those restrictions do not apply.

Physical extents mostly matters if you choose to create lots and lots of small logical volumes. In that case you might waste some disk space, if a physical extent is larger than your typical logical volume. On the other hand, choosing a very small PE size can slow down LVM tools during LVM operations (such as resizing a VG) quite a bit.

Nowadays I usually don't spend too much time on thinking about the PE size, I let my distro to choose it. If you have time and willingness, you can of course try different PE sizes and benchmark them to find out if PE size matters in your case.

Janne Pikkarainen
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  • with my 60GB ssd, choosing PE of 512MB leave me with 119 extents, but... I only intend to make at most 4 volumes and none with less than 512mb; so I guess I could use 512 PE as it may improve even more the seek performance? :) – Aquarius Power Feb 20 '15 at 16:27
  • I just saw this btw: http://serverfault.com/questions/279571/lvm-dangers-and-caveats; I think each extent may be mirrored to a raid if we want, and in this case, a 512MB PE could impact on performance; not sure tho. – Aquarius Power Feb 20 '15 at 16:30