[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM

Stuart Gathman stuart at gathman.org
Thu Apr 13 15:29:34 UTC 2017

On 04/13/2017 10:33 AM, Zdenek Kabelac wrote:
> Now when you have thin-pool - it cause quite a lot of trouble across
> number of layers.  There are solvable and being fixed.
> But as the rule #1 still applies - do not run your thin-pool out of
> space - it will not always heal easily without losing date - there is
> not a simple straighforward way how to fix it (especially when user
> cannot ADD any new space he promised to have) 
IMO, the friendliest thing to do is to freeze the pool in read-only mode
just before running out of metadata.  While still involving application
level data loss (the data it was just trying to write), and still
crashing the system (the system may be up and pingable and maybe even
sshable, but is "crashed" for normal purposes), it is simple to
understand and recover.   A sysadmin could have a plain LV for the
system volume, so that logs and stuff would still be kept, and admin
logins work normally.  There is no panic, as the data is there read-only.

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