From mboxrd@z Thu Jan 1 00:00:00 1970 References: <4b4d56ef-3127-212b-0e68-00b595faa241@redhat.com> <0535f3d744145eceea9121b1e68b622d@assyoma.it> <4fb6f017d9734892eff6b0ef544d99fc@assyoma.it> <20ddda25-dacf-f4e2-8df4-f9bed1c62fe7@redhat.com> <921a6b9c-103e-3c71-97d2-44ceb5a6bf87@redhat.com> <20170512134157.GA2523@nim> <5358d81c-bc94-8ce1-24e1-a5795502fffc@assyoma.it> From: Zdenek Kabelac Message-ID: <24d541f6-2c99-2c39-f398-6290275f0430@redhat.com> Date: Mon, 15 May 2017 17:33:19 +0200 MIME-Version: 1.0 In-Reply-To: <5358d81c-bc94-8ce1-24e1-a5795502fffc@assyoma.it> Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Snapshot behavior on classic LVM vs ThinLVM Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Gionatan Danti , linux-lvm@redhat.com 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 > logic." > > 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 > "ro,norecovery"). > > 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.... Regards Zdenek