[linux-lvm] Why is the performance of my lvmthin snapshot so poor

Demi Marie Obenour demi at invisiblethingslab.com
Wed Jun 15 16:39:03 UTC 2022

On Wed, Jun 15, 2022 at 02:40:29PM +0200, Gionatan Danti wrote:
> Il 2022-06-15 11:46 Zhiyong Ye ha scritto:
> > I also think it meets expectations. But is there any other way to
> > optimize snapshot performance at the code level? Does it help to
> > reduce the chunksize size in the code, I see in the help documentation
> > that the chunksize can only be 64k minimum.
> I don't think forcing the code to use smaller recordsize is a good idea.
> Considering the hard limit on metadata size (16 GB max), 64K chunks are good
> for ~16 TB thin pool - already relatively small.
> A, say, 16K recordsize would be good for a 4 TB pool only, an so on.
> Moreover, sequential performance will significantly suffer.
> I think you have to accept the performance hit on first chunck allocation &
> rewrite.

I seriously hope this will be fixed in dm-thin v2.  It’s a significant
problem for Qubes OS.

Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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