From: Marcelo Tosatti <mtosatti@redhat.com> To: Stefan Hajnoczi <stefanha@gmail.com> Cc: dlaor@redhat.com, Kevin Wolf <kwolf@redhat.com>, Chris Wright <chrisw@redhat.com>, KVM devel mailing list <kvm@vger.kernel.org>, quintela@redhat.com, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>, jes sorensen <jes.sorensen@redhat.com> Subject: Re: [Qemu-devel] KVM call agenda for June 28 Date: Tue, 5 Jul 2011 09:58:58 -0300 [thread overview] Message-ID: <20110705125858.GA21254@amt.cnet> (raw) In-Reply-To: <CAJSP0QXLJBZn_3RfCWJCBE8-6LMd2jn4gJ3DqM8VHG3gg+85iQ@mail.gmail.com> On Tue, Jul 05, 2011 at 01:40:08PM +0100, Stefan Hajnoczi wrote: > On Tue, Jul 5, 2011 at 9:01 AM, Dor Laor <dlaor@redhat.com> wrote: > > I tried to re-arrange all of the requirements and use cases using this wiki > > page: http://wiki.qemu.org/Features/LiveBlockMigration > > > > It would be the best to agree upon the most interesting use cases (while we > > make sure we cover future ones) and agree to them. > > The next step is to set the interface for all the various verbs since the > > implementation seems to be converging. > > Live block copy was supposed to support snapshot merge. I think the > current favored approach is to make the source image a backing file to > the destination image and essentially do image streaming. > > Using this mechanism for snapshot merge is tricky. The COW file > already uses the read-only snapshot base image. So now we cannot > trivally copy the COW file contents back into the snapshot base image > using live block copy. It never did. Live copy creates a new image were both snapshot and "current" are copied to. This is similar with image streaming. > It seems like snapshot merge will require dedicated code that reads > the allocated clusters from the COW file and writes them back into the > base image. > > A very inefficient alternative would be to create a third image, the > "merge" image file, which has the COW file as its backing file: > snapshot (base) -> cow -> merge > > All data from snapshot and cow is copied into merge and then snapshot > and cow can be deleted. But this approach is results in full data > copying and uses potentially 3x space if cow is close to the size of > snapshot. Management can set a higher limit on the size of data that is merged, and create a new base once exceeded. This avoids copying excessive amounts of data. > Any other ideas that reuse live block copy for snapshot merge? > > Stefan
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com> To: Stefan Hajnoczi <stefanha@gmail.com> Cc: Kevin Wolf <kwolf@redhat.com>, Chris Wright <chrisw@redhat.com>, KVM devel mailing list <kvm@vger.kernel.org>, quintela@redhat.com, jes sorensen <jes.sorensen@redhat.com>, dlaor@redhat.com, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com> Subject: Re: [Qemu-devel] KVM call agenda for June 28 Date: Tue, 5 Jul 2011 09:58:58 -0300 [thread overview] Message-ID: <20110705125858.GA21254@amt.cnet> (raw) In-Reply-To: <CAJSP0QXLJBZn_3RfCWJCBE8-6LMd2jn4gJ3DqM8VHG3gg+85iQ@mail.gmail.com> On Tue, Jul 05, 2011 at 01:40:08PM +0100, Stefan Hajnoczi wrote: > On Tue, Jul 5, 2011 at 9:01 AM, Dor Laor <dlaor@redhat.com> wrote: > > I tried to re-arrange all of the requirements and use cases using this wiki > > page: http://wiki.qemu.org/Features/LiveBlockMigration > > > > It would be the best to agree upon the most interesting use cases (while we > > make sure we cover future ones) and agree to them. > > The next step is to set the interface for all the various verbs since the > > implementation seems to be converging. > > Live block copy was supposed to support snapshot merge. I think the > current favored approach is to make the source image a backing file to > the destination image and essentially do image streaming. > > Using this mechanism for snapshot merge is tricky. The COW file > already uses the read-only snapshot base image. So now we cannot > trivally copy the COW file contents back into the snapshot base image > using live block copy. It never did. Live copy creates a new image were both snapshot and "current" are copied to. This is similar with image streaming. > It seems like snapshot merge will require dedicated code that reads > the allocated clusters from the COW file and writes them back into the > base image. > > A very inefficient alternative would be to create a third image, the > "merge" image file, which has the COW file as its backing file: > snapshot (base) -> cow -> merge > > All data from snapshot and cow is copied into merge and then snapshot > and cow can be deleted. But this approach is results in full data > copying and uses potentially 3x space if cow is close to the size of > snapshot. Management can set a higher limit on the size of data that is merged, and create a new base once exceeded. This avoids copying excessive amounts of data. > Any other ideas that reuse live block copy for snapshot merge? > > Stefan
next prev parent reply other threads:[~2011-07-05 12:59 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-06-27 14:32 KVM call agenda for June 28 Juan Quintela 2011-06-27 14:32 ` [Qemu-devel] " Juan Quintela 2011-06-28 13:38 ` Stefan Hajnoczi 2011-06-28 13:38 ` [Qemu-devel] " Stefan Hajnoczi 2011-06-28 19:41 ` Marcelo Tosatti 2011-06-28 19:41 ` [Qemu-devel] " Marcelo Tosatti 2011-06-29 5:32 ` Stefan Hajnoczi 2011-06-29 5:32 ` [Qemu-devel] " Stefan Hajnoczi 2011-06-29 7:57 ` Kevin Wolf 2011-06-29 7:57 ` [Qemu-devel] " Kevin Wolf 2011-06-29 10:08 ` Stefan Hajnoczi 2011-06-29 10:08 ` [Qemu-devel] " Stefan Hajnoczi 2011-06-29 15:41 ` Marcelo Tosatti 2011-06-29 15:41 ` [Qemu-devel] " Marcelo Tosatti 2011-06-30 11:48 ` Stefan Hajnoczi 2011-06-30 11:48 ` [Qemu-devel] " Stefan Hajnoczi 2011-06-30 12:39 ` Kevin Wolf 2011-06-30 12:39 ` [Qemu-devel] " Kevin Wolf 2011-06-30 12:54 ` Stefan Hajnoczi 2011-06-30 12:54 ` [Qemu-devel] " Stefan Hajnoczi 2011-06-30 14:36 ` Marcelo Tosatti 2011-06-30 14:36 ` [Qemu-devel] " Marcelo Tosatti 2011-06-30 14:52 ` Kevin Wolf 2011-06-30 14:52 ` [Qemu-devel] " Kevin Wolf 2011-06-30 18:38 ` Marcelo Tosatti 2011-07-05 8:01 ` Dor Laor 2011-07-05 12:40 ` Stefan Hajnoczi 2011-07-05 12:40 ` Stefan Hajnoczi 2011-07-05 12:58 ` Marcelo Tosatti [this message] 2011-07-05 12:58 ` Marcelo Tosatti 2011-07-05 13:39 ` Dor Laor 2011-07-05 13:39 ` Dor Laor 2011-07-05 14:29 ` Marcelo Tosatti 2011-07-05 14:29 ` [Qemu-devel] " Marcelo Tosatti 2011-07-05 14:32 ` Marcelo Tosatti 2011-07-05 14:32 ` Marcelo Tosatti 2011-07-05 14:46 ` Kevin Wolf 2011-07-05 14:46 ` Kevin Wolf 2011-07-05 15:04 ` Dor Laor 2011-07-05 15:04 ` Dor Laor 2011-07-05 15:29 ` Marcelo Tosatti 2011-07-05 15:29 ` Marcelo Tosatti 2011-07-05 15:37 ` Stefan Hajnoczi 2011-07-05 15:37 ` Stefan Hajnoczi 2011-07-05 18:18 ` Marcelo Tosatti 2011-07-05 18:18 ` Marcelo Tosatti 2011-07-06 7:48 ` Kevin Wolf 2011-07-06 7:48 ` Kevin Wolf 2011-07-07 15:25 ` Stefan Hajnoczi 2011-07-07 15:25 ` Stefan Hajnoczi 2011-06-28 13:43 ` Anthony Liguori 2011-06-28 13:43 ` Anthony Liguori 2011-06-28 13:48 ` Avi Kivity 2011-06-28 13:48 ` Avi Kivity 2011-06-30 14:10 ` Anthony Liguori
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