How can I restripe LVs on addition of extra PVs?
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Quoted 19 lines · Clint Byrum
Quoted 11 lines · Daniel .
Hi,
[I'm only familiar with LVM1, so that's what I'm referring to in the rest of the mail. I probably could move to LVM2 if it solves my problems.]
I'm planning on using LVM to create LVs striped across multiple PVs (which, incidentally, are RAID 1 mirrorred partitions). In the future I will need to add extra PVs to the VG and extend the LVs.
This just came up in #lvm on freenode today. I don't think this is at all possible with LVM1. Once the striping is done for an LV, that LV cannot be extended past the physical extents that were allocated at that time.
Quoted 7 lines
However, with LVM2, you could write a script to do this by manually running pvmove over and over, doing something like "pvmove dev:1-8 otherdev;pvmove otherdev:1-8 dev;" .. It gets rather complex to figure this out on the cmdline, but I do believe it can be done and you would end up with PE's evenly spread out over all PVs.
Somebody tell me this is wrong and stupid before I try it. ;)
One problem I see with doing this is that your LVM metadata is going to get rather large after you've done this. Because you're mucking with the segments through pvmove, lvm doesn't know that you're trying to convert a stripe set of 2 to a stripe set of 4 or whatever. I'm not positive, but it seems like this could be a problem.
Also, remember that stripe size is different then segment size, and segment size is the level at which pvmove manipulates things. So that's probably not going to do what you want it to.
Regards,
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