On 11/10/2011 04:41 AM, Kevin Wolf wrote:
Am 09.11.2011 22:01, schrieb Anthony Liguori:
On 11/09/2011 03:00 PM, Michael S. Tsirkin wrote:
On Wed, Nov 09, 2011 at 02:22:02PM -0600, Anthony Liguori wrote:
On 11/09/2011 02:18 PM, Michael S. Tsirkin wrote:
On Wed, Nov 09, 2011 at 11:35:54AM -0600, Anthony Liguori wrote:
On 11/09/2011 11:02 AM, Avi Kivity wrote:
On 11/09/2011 06:39 PM, Anthony Liguori wrote:
Migration with qcow2 is not a supported feature for 1.0. Migration is
only supported with raw images using coherent shared storage[1].
[1] NFS is only coherent with close-to-open which right now is not
good enough for migration.
Say what?
Due to block format probing, we read at least the first sector of
the disk during start up.
A simple solution is not to do any probing before the VM is first
started on the incoming path.
Any issues with this?
http://mid.gmane.org/1284213896-12705-4-git-send-email-aliguori@xxxxxxxxxx
I think Kevin wanted open to get delayed.
Regards,
Anthony Liguori
So, this patchset just needs to be revived and polished up?
What I took from the feedback was that Kevin wanted to defer open until the
device model started. That eliminates the need to reopen or have a invalidation
callback.
I think it would be good for Kevin to comment here though because I might have
misunderstood his feedback.
Your approach was to delay reads, but still keep the image open. I think
I worried that we might have additional reads somewhere that we don't
know about, and this is why I proposed delaying the open as well, so
that any read would always fail.
I believe just reopening the image is (almost?) as good and it's way
easier to do, so I would be inclined to do that for 1.0.
I don't think reopen is good enough without delaying CHS probing too. That
information is still potentially out of date. I don't think you can fix this
problem without delaying CHS probing at least.
Regards,
Anthony Liguori
I'm not 100% sure about cases like iscsi, where reopening doesn't help.
I think delaying the open doesn't help there either if you migrate from
A to B and then back from B to A, you could still get old data. So for
iscsi probably cache=none remains the only safe choice, whatever we do.
Kevin
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