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

Zdenek Kabelac zkabelac at redhat.com
Thu Mar 1 16:00:17 UTC 2018

Dne 1.3.2018 v 13:48 Gionatan Danti napsal(a):
> On 01/03/2018 12:23, Zdenek Kabelac wrote:
>> In general - for extX  it's remount read-only upon error - which works for 
>> journaled metadata - if you want same protection for 'data' you need to 
>> switch to rather expensive data journaling mode.
>> For XFS there is now similar logic where write error on journal stops 
>> filesystem usage - look far some older message (even here in this list) it's 
>> been mentioned already few times I guess...

There is quite 'detailed' config for XFS - just not all settings
are probably tuned in the best way for provisioning.



>> Unfreezed filesystem is simply not usable...
> I was speaking about unfreezed thin metadata snapshot - ie: 
> reserve_metadata_snap *without* a corresponding release_metadata_snap. Will 
> that cause problems?

metadata snapshot 'just consumes' thin-pool metadata space,
at any time there can be only 1 snapshot - so before next usage
you have to drop the existing one.

So IMHO it should have no other effects unless you hit some bugs...

> I think VDO is a fruit of Permabit acquisition, right? As it implements it's 
> own thin provisioning, will thinlvm migrate to VDO or it will continue to use 
> the current dmtarget?

thin-pool  target is having different goals then VDO
so both targets will likely live together.

Possibly thin-pool might be tested for using VDO data volume if it makes any 



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