[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM
zkabelac at redhat.com
Wed Apr 26 07:42:46 UTC 2017
Dne 26.4.2017 v 09:26 Gionatan Danti napsal(a):
> Il 24-04-2017 23:59 Zdenek Kabelac ha scritto:
>> If you set '--errorwhenfull y' - it should instantly fail.
> It's my understanding that "--errorwhenfull y" will instantly fail writes
> which imply new allocation requests, but writes to already-allocated space
> will be completed.
yes you understand it properly.
> It is possible, without messing directly with device mapper (via dmsetup), to
> configure a strict "read-only" policy, where *all* writes (both to allocated
> or not allocated space) will fail?
Nope it's not.
> It is not possible to do via lvm tools, what/how device-mapper target should
> be used?
At this moment it's not possible.
I do have some plans/idea how to workaround this in user-space but it's
non-trivial - especially on recovery path.
It would be possible to 'reroute' thin to dm-delay and then write path to
error and read path leave as is - but it's adding many new states to handle,
to ATM it's in queue...
Using 'ext4' with remount-ro is fairly easy to setup and get exactly this
More information about the linux-lvm