[Qemu-devel] drive-mirror sync points
Paolo/anyone who knows - Are drive-mirror sync points (NBD flush commands) reflecting guest write barriers? Are guest write barriers respected by drive-mirror? If so, that would make drive-mirror much more palatable for disk introspection work (a drop-in usable feature of QEMU!). -- Wolf
Re: [Qemu-devel] drive-mirror sync points
Il 13/05/2013 19:50, Wolfgang Richter ha scritto: Paolo/anyone who knows - Are drive-mirror sync points (NBD flush commands) reflecting guest write barriers? Are guest write barriers respected by drive-mirror? If so, that would make drive-mirror much more palatable for disk introspection work (a drop-in usable feature of QEMU!). Kind of. Sync points reflect points where the destination image is a copy of the source image at some point in time. Destination image write barriers hence reflect places where the destination image is consistent with guest write barriers, but not all guest write barriers become destination image write barriers. Paolo
Re: [Qemu-devel] drive-mirror sync points
On Mon, May 13, 2013 at 01:50:00PM -0400, Wolfgang Richter wrote: Paolo/anyone who knows - Are drive-mirror sync points (NBD flush commands) reflecting guest write barriers? Are guest write barriers respected by drive-mirror? If so, that would make drive-mirror much more palatable for disk introspection work (a drop-in usable feature of QEMU!). I'm also interested in this question. Further extensions to this (*not* drive-mirror on its own AIUI) which stefanha is working on should allow libguestfs to perform point-in-time snapshots of images, which will mean that we can do complex and long-running inspection operations on live guests. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top
Re: [Qemu-devel] drive-mirror sync points
On Mon, May 13, 2013 at 10:46:55PM +0100, Richard W.M. Jones wrote: On Mon, May 13, 2013 at 01:50:00PM -0400, Wolfgang Richter wrote: Paolo/anyone who knows - Are drive-mirror sync points (NBD flush commands) reflecting guest write barriers? Are guest write barriers respected by drive-mirror? If so, that would make drive-mirror much more palatable for disk introspection work (a drop-in usable feature of QEMU!). I'm also interested in this question. Further extensions to this (*not* drive-mirror on its own AIUI) which stefanha is working on should allow libguestfs to perform point-in-time snapshots of images, which will mean that we can do complex and long-running inspection operations on live guests. OK, I got my attributions wrong there. I see that Dietmar Maurer wrote the original version of the patch and Stefan modified that. Anyway I'm very interested in point-in-time snapshots. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#)
Re: [Qemu-devel] drive-mirror sync points
On May 13, 2013, at 5:46 PM, Richard W.M. Jones rjo...@redhat.com wrote: On Mon, May 13, 2013 at 01:50:00PM -0400, Wolfgang Richter wrote: Paolo/anyone who knows - Are drive-mirror sync points (NBD flush commands) reflecting guest write barriers? Are guest write barriers respected by drive-mirror? If so, that would make drive-mirror much more palatable for disk introspection work (a drop-in usable feature of QEMU!). I'm also interested in this question. Further extensions to this (*not* drive-mirror on its own AIUI) which stefanha is working on should allow libguestfs to perform point-in-time snapshots of images, which will mean that we can do complex and long-running inspection operations on live guests. And I'm trying to do complex, long-running inspection on live guests without needing point-in-time snapshots :-)
