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Re: [linux-lvm] Convert striped lv to single pv on another disk?



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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