Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 11:46:15PM +0200, Paolo Bonzini wrote: > Il 22/05/2013 22:47, Richard W.M. Jones ha scritto: > >> > > >> > I meant if there was interest in reading from a disk that isn't fully > >> > synchronized > >> > (yet) to the original disk (it might have old blocks). Or would you o

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 22/05/2013 22:47, Richard W.M. Jones ha scritto: >> > >> > I meant if there was interest in reading from a disk that isn't fully >> > synchronized >> > (yet) to the original disk (it might have old blocks). Or would you only >> > want to >> > connect once a (complete) snapshot is available (sy

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 03:38:33PM -0400, Wolfgang Richter wrote: > On Wed, May 22, 2013 at 3:26 PM, Richard W.M. Jones wrote: > > > On Wed, May 22, 2013 at 02:32:37PM -0400, Wolfgang Richter wrote: > > > On Wed, May 22, 2013 at 12:42 PM, Richard W.M. Jones > >wrote: > > > > > > > Run up to two e

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 3:26 PM, Richard W.M. Jones wrote: > On Wed, May 22, 2013 at 02:32:37PM -0400, Wolfgang Richter wrote: > > On Wed, May 22, 2013 at 12:42 PM, Richard W.M. Jones >wrote: > > > > > Run up to two extra guestfish instances, with the same result. The > > > fourth guestfish inst

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 02:32:37PM -0400, Wolfgang Richter wrote: > On Wed, May 22, 2013 at 12:42 PM, Richard W.M. Jones wrote: > > > Run up to two extra guestfish instances, with the same result. The > > fourth guestfish instance hangs at the 'run' command until one of the > > first three is tol

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 12:42 PM, Richard W.M. Jones wrote: > Run up to two extra guestfish instances, with the same result. The > fourth guestfish instance hangs at the 'run' command until one of the > first three is told to exit. And your interested on being notified when a snapshot is "safe"

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 11:51:16AM -0400, Wolfgang Richter wrote: > This is actually interesting. Does the QEMU nbd server support multiple > readers? Yes. qemu-nbd has a -e/--shared= option which appears to do exactly what it says in the man page. $ guestfish -N fs exit $ ls -lh test1.img -rw

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 22, 2013 at 12:11 PM, Paolo Bonzini wrote: > > Essentially, if you're RWMJ (not me), and you're keeping a full > > mirror, it's clear that the mirror write stream goes to an nbd server, > > but is it possible to attach a reader to that same nbd server and read > > things back (read-on

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 22/05/2013 17:51, Wolfgang Richter ha scritto: > On Thu, May 16, 2013 at 9:44 AM, Richard W.M. Jones > wrote: > > Ideally I'd like to issue some QMP commands which would set up the > point-in-time snapshot, and then connect to this snapshot over (eg) > NBD

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Thu, May 16, 2013 at 9:44 AM, Richard W.M. Jones wrote: > Ideally I'd like to issue some QMP commands which would set up the > point-in-time snapshot, and then connect to this snapshot over (eg) > NBD, then when I'm done, send some more QMP commands to tear down the snapshot. > This is actual

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Wed, May 15, 2013 at 7:54 AM, Paolo Bonzini wrote: > > But does this really cover all use cases a real synchronous active > > mirror would provide? I understood that Wolf wants to get every single > > guest request exposed e.g. on an NBD connection. > > He can use throttling to limit the guest

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

[...] >From my point of view, what I'm missing here is how would I use it. Ideally I'd like to issue some QMP commands which would set up the point-in-time snapshot, and then connect to this snapshot over (eg) NBD, then when I'm done, send some more QMP commands to tear down the snapshot. I thin

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 15/05/2013 11:46, Kevin Wolf ha scritto: > Am 15.05.2013 um 11:16 hat Paolo Bonzini geschrieben: > Does the "if there was no room" part mean that the mirror is active only > sometimes? Yes, otherwise the guest can allocate arbitrary amounts of memory in the host just by st

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Am 15.05.2013 um 11:16 hat Paolo Bonzini geschrieben: > > > > Does the "if there was no room" part mean that the mirror is active only > > > > sometimes? > > > > > > Yes, otherwise the guest can allocate arbitrary amounts of memory in the > > > host just by starting a few very large I/O operations

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

> > We don't need a way to pass data from before to after hooks, a simple > > scan of a linked list will do. > > So in this case the linked list is the way. Point taken. :) > > > Does the "if there was no room" part mean that the mirror is active only > > > sometimes? > > > > Yes, otherwise th

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Am 15.05.2013 um 10:25 hat Paolo Bonzini geschrieben: > Il 15/05/2013 09:59, Kevin Wolf ha scritto: > >>> Do you mean you'd model the 'active' mode after 'block-backup,' or > >>> actually > >>> call functions provided by 'block-backup'? > >> > >> No, I'll just reuse the same hooks within block/mir

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 15/05/2013 09:59, Kevin Wolf ha scritto: >>> Do you mean you'd model the 'active' mode after 'block-backup,' or actually >>> call functions provided by 'block-backup'? >> >> No, I'll just reuse the same hooks within block/mirror.c (almost... it >> looks like I need after_write too, not just befo

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Am 14.05.2013 um 18:45 hat Paolo Bonzini geschrieben: > Il 14/05/2013 17:48, Wolfgang Richter ha scritto: > > On Tue, May 14, 2013 at 6:04 AM, Paolo Bonzini > > wrote: > > > > Il 14/05/2013 10:50, Kevin Wolf ha scritto: > > > Or, to translate it into our existi

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Tue, May 14, 2013 at 12:45 PM, Paolo Bonzini wrote: > No, I'll just reuse the same hooks within block/mirror.c (almost... it > looks like I need after_write too, not just before_write :( that's a > pity). Basically: > > 1) before the write, if there is space in the job's buffers, allocate a >

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 14/05/2013 17:48, Wolfgang Richter ha scritto: > On Tue, May 14, 2013 at 6:04 AM, Paolo Bonzini > wrote: > > Il 14/05/2013 10:50, Kevin Wolf ha scritto: > > Or, to translate it into our existing terminology, drive-mirror > > implements a passive mirror,

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Tue, May 14, 2013 at 6:04 AM, Paolo Bonzini wrote: > Il 14/05/2013 10:50, Kevin Wolf ha scritto: > > Or, to translate it into our existing terminology, drive-mirror > > implements a passive mirror, you're proposing an active one (which we > > do want to have). > > > > With an active mirror, we

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Tue, May 14, 2013 at 4:50 AM, Kevin Wolf wrote: > Or, to translate it into our existing terminology, drive-mirror > implements a passive mirror, you're proposing an active one (which we > do want to have). > > With an active mirror, we'll want to have another choice: The mirror can > be synchr

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Tue, May 14, 2013 at 4:40 AM, Stefan Hajnoczi wrote: > QEMU is accumulating many different approaches to snapshots and > mirroring. They all have their pros and cons so it's not possible to > support only one approach for all use cases. > > The suggested approach is writing a BlockDriver which

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Il 14/05/2013 10:50, Kevin Wolf ha scritto: > Or, to translate it into our existing terminology, drive-mirror > implements a passive mirror, you're proposing an active one (which we > do want to have). > > With an active mirror, we'll want to have another choice: The mirror can > be synchronous (g

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

Am 13.05.2013 um 23:21 hat Wolfgang Richter geschrieben: > I'm working on a new patch series which will add a new QMP command, > block-trace, which turns on tracing of writes for a specified block device and > sends the stream unmodified to another block device.  The 'trace' is meant to > be precis

Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

On Mon, May 13, 2013 at 05:21:54PM -0400, Wolfgang Richter wrote: > I'm working on a new patch series which will add a new QMP command, > block-trace, which turns on tracing of writes for a specified block device > and > sends the stream unmodified to another block device. The 'trace' is meant > t

[Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

I'm working on a new patch series which will add a new QMP command, block-trace, which turns on tracing of writes for a specified block device and sends the stream unmodified to another block device. The 'trace' is meant to be precise meaning that writes are not lost, which differentiates this com