[Gllug] LVM defrag

[James Hawtin]

On Thu, Mar 05, 2009 at 12:02:15AM +0000, Nix wrote:
> On 3 Mar 2009, Matthew King stated:
> 
> > In a similar vein to the previous thread, is there / has anyone heard of
> > a tool to defragment lvm volumes (or just generally move things around
> > without having to use pvmove directly)?
> 
> I've looked for them, but all I've heard was 'use pvmove'. Which is
> boring.

"Defraging" using pvmove on lvm1 is possible, however be verycareful on lvm2
it uses range based meta data and doing lots of single block moves can
result in a meta data explosition in /etc, I had a program to interlace
block accross multiple disks to spread the load on a san, which was fine on 
lvm1 on lvm2 it filled /etc

I would however question how necessary defraging really is, having a file
system comming from 2-3 sections of a disk will not cause to many problems,
having it fragmented over multiple disks will make (potentally faster). OF
course also increasing the chance of failer of any one drive.

James 
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