[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM
g.danti at assyoma.it
Mon Mar 5 14:27:09 UTC 2018
On 05/03/2018 11:18, Zdenek Kabelac wrote:
> Yes - it has been updated/improved/fixed - and I've already given you a
> link where you can configure the behavior of XFS when i.e. device
> reports ENOSPC to the filesystem.
Sure - I already studied it months ago during my testing. I simply was
under the impression that dm & xfs teams have different point of view
regarding the actual status. I'm happy to know that it isn't the case :)
> Well complexity - it might look 'easy' to do on the first sight, but in
> reality it's impacting all hot/fast paths with number of checks and it
> would have rather dramatic performance impact.
> The other case is, while for lots of filesystems it might look like best
> thing - it's not always true - so there are case where it's more desired
> to have still working device with 'several' failing piece in it...
> And 3rd moment is - it's unclear from kernel POV - where this 'full'
> pool moment actually happens - i.e. imagine running 'write' operation
> on one thin device and 'trim/discard' operation running on 2nd. device.
> So it's been left on user-space to solve the case the best way -
> i.e. user-space can initiate 'fstrim' itself when full pool case
> happens or get the space by number of other ways...
Ok, I see.
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