From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: LVM snapshot broke between 4.14 and 4.16 Date: Sat, 4 Aug 2018 14:18:47 -0400 Message-ID: <20180804181845.GA10499@redhat.com> References: <1ec0a220-d5b0-1c27-e63b-c4d3f4ce9d77@torlan.ru> <20180803185431.GB3258@redhat.com> <20180803193037.GA4581@redhat.com> <20180804052033.GA4461@thunk.org> <102c2d75-f768-a649-52c3-bac6f0ca738d@redhat.com> <20180804162205.GB4461@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180804162205.GB4461@thunk.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: "Theodore Y. Ts'o" Cc: Jens Axboe , Sagi Grimberg , Linux Kernel Mailing List , linux-block , dm-devel@redhat.com, Zdenek Kabelac , Ilya Dryomov , Linus Torvalds , wgh@torlan.ru List-Id: dm-devel.ids On Sat, Aug 04 2018 at 12:22pm -0400, Theodore Y. Ts'o wrote: > On Sat, Aug 04, 2018 at 10:36:50AM +0200, Zdenek Kabelac wrote: > > dm-snapshost has really outdated design - it's been useful in the old age > > where megabyte was hell lot of space. > > > > Nowadays, when users do need to handle snapshots in multi gigabyte sizes and > > moreover have number of snapshots from the same volume taken over the time, > > want to take snapshot of snapshot of snapshot, the old snapshot simple kills > > all the performance, uses tons of resources and becomes serious bottleneck > > of your system and has lots of usability limitation. > > Fair enough. I don't think I would consider that makes dm-snapshot a > "steaming pile". For me, protection against data loss is Job One. What's your point Ted? Do you have _any_ intention of actually using anything DM or is this just a way for you to continue to snipe at it? > > That's where thin provisioning will shine.... > > The dm-thin development might want to take a look at what's currently > in Documentation/device-mapper/thin-privisioning.txt: > > Status > ====== > > These targets are very much still in the EXPERIMENTAL state. Please > do not yet rely on them in production. But do experiment and offer us > feedback. Different use cases will have different performance > characteristics, for example due to fragmentation of the data volume. > > If you find this software is not performing as expected please mail > dm-devel@redhat.com with details and we'll try our best to improve > things for you. > > Userspace tools for checking and repairing the metadata are under > development. > > Saying that dm-snapshot is a steaming pile and dm-thin is what > everyone should use doesn't seem to be consistent with the above. Maybe read your email from earlier today before repeating yourself: https://lkml.org/lkml/2018/8/4/366 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sat, 4 Aug 2018 14:18:47 -0400 From: Mike Snitzer To: "Theodore Y. Ts'o" Cc: Zdenek Kabelac , Linus Torvalds , Jens Axboe , Sagi Grimberg , Linux Kernel Mailing List , linux-block , dm-devel@redhat.com, Ilya Dryomov , wgh@torlan.ru Subject: Re: LVM snapshot broke between 4.14 and 4.16 Message-ID: <20180804181845.GA10499@redhat.com> References: <1ec0a220-d5b0-1c27-e63b-c4d3f4ce9d77@torlan.ru> <20180803185431.GB3258@redhat.com> <20180803193037.GA4581@redhat.com> <20180804052033.GA4461@thunk.org> <102c2d75-f768-a649-52c3-bac6f0ca738d@redhat.com> <20180804162205.GB4461@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180804162205.GB4461@thunk.org> List-ID: On Sat, Aug 04 2018 at 12:22pm -0400, Theodore Y. Ts'o wrote: > On Sat, Aug 04, 2018 at 10:36:50AM +0200, Zdenek Kabelac wrote: > > dm-snapshost has really outdated design - it's been useful in the old age > > where megabyte was hell lot of space. > > > > Nowadays, when users do need to handle snapshots in multi gigabyte sizes and > > moreover have number of snapshots from the same volume taken over the time, > > want to take snapshot of snapshot of snapshot, the old snapshot simple kills > > all the performance, uses tons of resources and becomes serious bottleneck > > of your system and has lots of usability limitation. > > Fair enough. I don't think I would consider that makes dm-snapshot a > "steaming pile". For me, protection against data loss is Job One. What's your point Ted? Do you have _any_ intention of actually using anything DM or is this just a way for you to continue to snipe at it? > > That's where thin provisioning will shine.... > > The dm-thin development might want to take a look at what's currently > in Documentation/device-mapper/thin-privisioning.txt: > > Status > ====== > > These targets are very much still in the EXPERIMENTAL state. Please > do not yet rely on them in production. But do experiment and offer us > feedback. Different use cases will have different performance > characteristics, for example due to fragmentation of the data volume. > > If you find this software is not performing as expected please mail > dm-devel@redhat.com with details and we'll try our best to improve > things for you. > > Userspace tools for checking and repairing the metadata are under > development. > > Saying that dm-snapshot is a steaming pile and dm-thin is what > everyone should use doesn't seem to be consistent with the above. Maybe read your email from earlier today before repeating yourself: https://lkml.org/lkml/2018/8/4/366