[linux-lvm] lvremove does not pass discards if volume is part of thin pool
Tomas Janousek
tomi at nomi.cz
Fri Jan 22 17:18:29 UTC 2016
Hello all,
On Wed, Aug 19, 2015 at 01:40:08PM +0300, vaLentin chernoZemski wrote:
> I just tested my case with LVM2.2.02.128 with the latest kernel 4.1.6 and it
> still does not work.
>
> [...]
>
> Let me know if you need anything else that could help us debug this issue
> and fix it.
Has there been any progress here? I'm experiencing the same issue here with
kernel 4.4.0 and lvm:
lvm> version
LVM version: 2.02.138(2) (2015-12-14)
Library version: 1.02.114 (2015-12-14)
Driver version: 4.34.0
Is there perhaps some way to force the discard manually? I thought that maybe
creating a new sparse file/loop device/physical volume and doing pvmove might
help, but what I got instead was a file that wasn't sparse at all, actually
taking more space than the original one. Is this expected?
(The only explanation I can think of is that pvmove doesn't care nor
understand the on-disk format of device mapper thin-pools so it has to copy
everything byte by byte. Is that it?)
Maybe creating a sufficiently large volume in the thin pool, doing a dd
if=/dev/zero of=/path/to/volume/tmp/blanks and then deleting
/path/to/volume/tmp/blanks would help, but could be quite slow. :-(
Regards,
--
Tomáš Janoušek, a.k.a. Pivník, a.k.a. Liskni_si, http://work.lisk.in/
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