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

Gionatan Danti g.danti at assyoma.it
Tue May 16 13:38:56 UTC 2017

On 16/05/2017 12:54, Zdenek Kabelac wrote:
> Hi
> Somehow I think you've rather made a mistake during your test (or you 
> have buggy kernel). Can you take full log of your test  show all options 
> are
> properly applied
> i.e. dmesg log +  /proc/self/mountinfo report showing all options used 
> for mountpoint and kernel version in use.
> IMHO you should get something like this in dmesg once your pool gets out 
> of space and starts to return error on write:
> ----
> Aborting journal on device dm-4-8.
> EXT4-fs error (device dm-4): ext4_journal_check_start:60: Detected 
> aborted journal
> EXT4-fs (dm-4): Remounting filesystem read-only
> ----
> Clearly when you specify 'data=journal'  even write failure of data will 
> cause journal error and thus remount-ro reaction (it least on my box 
> does it) - but such usage is noticeable slower compared with 'ordered' 
> mode.

Zdenek, you are right: re-executing the test, I now see the following 
dmesg entries:

[ 1873.677882] Aborting journal on device dm-6-8.
[ 1873.757170] EXT4-fs error (device dm-6): ext4_journal_check_start:56: 
Detected aborted journal
[ 1873.757184] EXT4-fs (dm-6): Remounting filesystem read-only

At the same time, looking at bash history and /var/log/messages it 
*seems* that I did nothing wrong with previous tests. I'll do more tests 
and post here if I find something relevant.

Thanks for your time and patience.

Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti at assyoma.it - info at assyoma.it
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