[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-15 Thread Juan Quintela
Kevin Wolf wrote: > Am 11.09.2010 16:04, schrieb Anthony Liguori: >> This fixes a couple nasty problems relating to live migration. >> >> 1) When dealing with shared storage with weak coherence (i.e. NFS), even if >>we re-read, we may end up with undesired caching. By delaying any reads >>

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-15 Thread Juan Quintela
Anthony Liguori wrote: > On 09/12/2010 05:42 AM, Avi Kivity wrote: >> On 09/11/2010 05:04 PM, Anthony Liguori wrote: >>> This fixes a couple nasty problems relating to live migration. >>> >>> 1) When dealing with shared storage with weak coherence (i.e. NFS), >>> even if >>> we re-read, we ma

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-14 Thread Avi Kivity
On 09/14/2010 02:51 PM, Anthony Liguori wrote: On 09/14/2010 04:47 AM, Avi Kivity wrote: On 09/13/2010 04:34 PM, Anthony Liguori wrote: On 09/13/2010 09:13 AM, Kevin Wolf wrote: I think the only real advantage is that we fix NFS migration, right? That's the one that we know about, yes. The

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-14 Thread Anthony Liguori
On 09/14/2010 04:47 AM, Avi Kivity wrote: On 09/13/2010 04:34 PM, Anthony Liguori wrote: On 09/13/2010 09:13 AM, Kevin Wolf wrote: I think the only real advantage is that we fix NFS migration, right? That's the one that we know about, yes. The rest is not a specific scenario, but a strong fe

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-14 Thread Avi Kivity
On 09/13/2010 04:34 PM, Anthony Liguori wrote: On 09/13/2010 09:13 AM, Kevin Wolf wrote: I think the only real advantage is that we fix NFS migration, right? That's the one that we know about, yes. The rest is not a specific scenario, but a strong feeling that having an image opened twice at

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-14 Thread Kevin Wolf
Am 13.09.2010 22:09, schrieb Anthony Liguori: > On 09/13/2010 03:03 PM, Kevin Wolf wrote: >> Am 13.09.2010 21:29, schrieb Stefan Hajnoczi: >> >>> On Mon, Sep 13, 2010 at 3:13 PM, Kevin Wolf wrote: >>> Am 13.09.2010 15:42, schrieb Anthony Liguori: > On 09/13/2010 08:

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Anthony Liguori
On 09/13/2010 03:03 PM, Kevin Wolf wrote: Am 13.09.2010 21:29, schrieb Stefan Hajnoczi: On Mon, Sep 13, 2010 at 3:13 PM, Kevin Wolf wrote: Am 13.09.2010 15:42, schrieb Anthony Liguori: On 09/13/2010 08:39 AM, Kevin Wolf wrote: Yeah, one of the key design points of

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Kevin Wolf
Am 13.09.2010 21:29, schrieb Stefan Hajnoczi: > On Mon, Sep 13, 2010 at 3:13 PM, Kevin Wolf wrote: >> Am 13.09.2010 15:42, schrieb Anthony Liguori: >>> On 09/13/2010 08:39 AM, Kevin Wolf wrote: > Yeah, one of the key design points of live migration is to minimize the > number of failure sc

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Stefan Hajnoczi
On Mon, Sep 13, 2010 at 3:13 PM, Kevin Wolf wrote: > Am 13.09.2010 15:42, schrieb Anthony Liguori: >> On 09/13/2010 08:39 AM, Kevin Wolf wrote: Yeah, one of the key design points of live migration is to minimize the number of failure scenarios where you lose a VM.  If someone typed the >

Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Anthony Liguori
On 09/13/2010 09:13 AM, Kevin Wolf wrote: I think the only real advantage is that we fix NFS migration, right? That's the one that we know about, yes. The rest is not a specific scenario, but a strong feeling that having an image opened twice at the same time feels dangerous. We've neve

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Kevin Wolf
Am 13.09.2010 15:42, schrieb Anthony Liguori: > On 09/13/2010 08:39 AM, Kevin Wolf wrote: >>> Yeah, one of the key design points of live migration is to minimize the >>> number of failure scenarios where you lose a VM. If someone typed the >>> wrong command line or shared storage hasn't been mount

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Anthony Liguori
On 09/13/2010 08:39 AM, Kevin Wolf wrote: Yeah, one of the key design points of live migration is to minimize the number of failure scenarios where you lose a VM. If someone typed the wrong command line or shared storage hasn't been mounted yet and we delay failure until live migration is in the

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Kevin Wolf
Am 13.09.2010 15:29, schrieb Anthony Liguori: > On 09/13/2010 03:32 AM, Kevin Wolf wrote: >> Am 11.09.2010 16:04, schrieb Anthony Liguori: >> >>> This fixes a couple nasty problems relating to live migration. >>> >>> 1) When dealing with shared storage with weak coherence (i.e. NFS), even if >>

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Anthony Liguori
On 09/13/2010 03:32 AM, Kevin Wolf wrote: Am 11.09.2010 16:04, schrieb Anthony Liguori: This fixes a couple nasty problems relating to live migration. 1) When dealing with shared storage with weak coherence (i.e. NFS), even if we re-read, we may end up with undesired caching. By delayi

[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts

2010-09-13 Thread Kevin Wolf
Am 11.09.2010 16:04, schrieb Anthony Liguori: > This fixes a couple nasty problems relating to live migration. > > 1) When dealing with shared storage with weak coherence (i.e. NFS), even if >we re-read, we may end up with undesired caching. By delaying any reads >until we absolutely have