[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM
zkabelac at redhat.com
Mon May 15 15:33:19 UTC 2017
Dne 15.5.2017 v 16:48 Gionatan Danti napsal(a):
> On 15/05/2017 14:50, Zdenek Kabelac wrote> Hi
> What I does not understand is how XFS and EXT4 differs when a thinp is full.
> From a previous your reply, after I asked how to put thinp in read only mode
> when full:
> "Using 'ext4' with remount-ro is fairly easy to setup and get exactly this
> My naive interpretation is that when EXT4 detects *any* I/O error, it will set
> the filesystem in read-only mode. Except that my tests show that only failed
> *metadata* update put the filesystem in this state. The bad thingh is that,
> when not using "remount-ro", even failed metadata updates will *not* trigger
> any read-only response.
Ever tested this:
mount -o errors=remount-ro,data=journal ?
Everything has it's price - you want to have also 'safe' data - well you have
to pay the price.
> On the other hand, XFS has not such options but it, by default, ensures that
> failed *metadata* updates will stop the filesystem. Even reads are not allowed
> (to regain read access, you need to repair the filesystem or mount it with
> So, it should be even safer than EXT4, right? Or do you feel that is the other
> way around? If so, why?
I prefer 'remount-ro' as the FS is still at least accessible/usable in some way.
>> Things are getting better - but planning usage of thin-pool to 'recover'
>> overfilled pool is simple BAD planning. You should plan your thin-pool usage
>> to NOT run out-of-space.
> Sure, and I am *not* planning for it. But as bad things always happen, I'm
> preparing for them ;)
When you have extra space you can add for recovery - it's usually easy.
But you will have much harder time doing recovery without extra space.
So again - all has its price....
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