Re: silent data loss with ext4 / all current versions

On Fri, Nov 27, 2015 at 11:17 AM, Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> I plan to do more power failure testing soon, with more complex test
> scenarios. I suspect there might be other similar issues (e.g. when we
> rename a file before a checkpoint and don't fsync the directory - then the
> rename won't be replayed and will be lost).

I'm curious how you're doing this testing. The easiest way I can think
of would be to run a database on an LVM volume and take a large number
of LVM snapshots very rapidly and then see if the database can start
up from each snapshot. Bonus points for keeping track of the committed
transactions before each snaphsot and ensuring they're still there I
guess.

That always seemed unsatisfactory because in the past we were mainly
concerned with whether fsync was actually getting propagated to the
physical media. But for testing whether we're fsyncing enough for the
filesystem that would be good enough.

--
greg