[linux-lvm] Convert striped lv to single pv on another disk?
Stuart D Gathman
stuart at bmsi.com
Fri Dec 14 18:33:09 UTC 2012
On 12/13/2012 11:38 AM, Bryn M. Reeves expounded in part:
> On 13/12/12 16:11, Gianluca Cecchi wrote:
>> I found in another thread that the resulting LV with pvmove remains a
>> striped one on only one disk as far as its structure is concerned...
>> with degraded performance...
>> Have you an example of pvmove command options to test to execute based
>> on my test?
>> So that I can verify with my loop devices?
> Yes, you're right. You will end up with both stripes still present but
> on a single disk.
> The best I could do using pvmove was to move individual extents around
> (!) to make the LV contiguous on-disk. Of course, this doesn't remove
> the striping and inflates the number of segments since each pair of
> striped extents effectively becomes a segment.
> The lvconvert command also still accepts a -i <n> parameter but doesn't
> do anything useful with it and doesn't report an error.
Could you create an asymmetrical mirror - where one leg is striped and
the other is linear? Then you can just sync the mirror and delete the
striped leg. I could even see operating with such a mirror - call it
RAID ½. Reads would prefer the striped side, and the mirror is there in
case one of the stripes fails, while requiring only 1 additional drive
and degrading only write performance.
RAID10 over the 3 drives is probably better, though.
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