[linux-lvm] Testing ThinLVM metadata exhaustion

Gionatan Danti g.danti at assyoma.it
Tue Apr 26 07:11:53 UTC 2016

> bugzilla.redhat.com
> Anyway - 6.8 will likely be your solution.
> Thin-provisioning is NOT supposed to be used at 'corner' cases - we
> improve them, but older version simply had more of them as there was
> always clearly communicated do not over-provision if you can't provide
> the space.
> Out-of-space  is not equal if you run out of your filesystem space - you
> can't expect things will continue to work nicely - the cooperation of
> block layer with filesystem and metadata resilience are continually
> improved.
> We have actually even seen users 'targeting' to hit full-pool as a part
> of regular work-flow - bad bad plan...
> Regards
> Zdenek

[reposting due to sender error]

Hi Zdenek,
thanks for your courtesy.

I absolutely agree with you that in no case metadata exhaustion can be 
considered part of a "regular work-flow". At the same time, I often do 
"stress test" specifically crafted to put the software/hardware in the 
worst possible condition. In this manner, should an exceptionally bad 
situation occour, I know how to deal with it.

I have another question: does this bug only happen when metadata space 
is exausted? I am asking this because searching for other peoples with 
the same error message, I read this bug report: 

The bug described in the message above does not necessarily happen at 
metadata exaustion time, as confirmed here: 

I understand that these are old (2014) bugs and that were fixed in Linux 
3.14 but, using thin LVM volumes in production systems (albeit with RH 7 
only), I want to be reasonably sure that no show-stopper bug can hit me. 
Are current RH OSes (6.7 and 7.2) immune from this bug (metadata 
corruption even if tmeta is not full)?


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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