[linux-lvm] LVM and chain of snapshots

Alexander E. Patrakov patrakov at gmail.com
Wed Jan 20 13:02:04 UTC 2016

20.01.2016 17:09, Zdenek Kabelac wrote:
> Using lots of old-snaphosts is very bad plan - really time to look at
> thin-provisioning....
> Old-snaps are not going to scale.....

Well, I have already tried using lots of thin snapshots on my PC, in a 
context different from what Mark wants. Namely, my snapshots were 
created by Snapper, hourly.

Thin snapshots may indeed scale well for reads and writes, but currently 
they don't scale at all for the initial activation. The problem is that 
"vgchange -ay" and "vgchange -an", by default, run "thin_check", and the 
more snapshots I have, the more it takes for "thin_check" to finish. 
With 1 snapshot, it is quick enough so that I don't notice. But with, 
say, 200 snapshots (some of which include creation of an iso image), it 
takes more than 1.5 minutes - more than the initramfs (or myself) is 
going to wait during the boot process.

Alexander E. Patrakov

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