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Re: [libvirt] [Qemu-devel] qemu and qemu.git -> Migration + disk stress introduces qcow2 corruptions

On 11/11/2011 04:15 AM, Kevin Wolf wrote:
Am 10.11.2011 22:30, schrieb Anthony Liguori:
Live migration with qcow2 or any other image format is just not going to work
right now even with proper clustered storage.  I think doing a block level flush
cache interface and letting block devices decide how to do it is the best approach.

I would really prefer reusing the existing open/close code. It means
less (duplicated) code, is existing code that is well tested and doesn't
make migration much of a special case.

Just to be clear, reopen only addresses image format migration. It does not address NFS migration since it doesn't guarantee close-to-open semantics.

The problem I have with the reopen patches are that they introduce regressions and change at semantics for a management tool. If you look at the libvirt workflow with encrypted disks, it would break with the reopen patches.

If you want to avoid reopening the file on the OS level, we can reopen
only the topmost layer (i.e. the format, but not the protocol) for now
and in 1.1 we can use bdrv_reopen().

I don't view not supporting migration with image formats as a regression as it's never been a feature we've supported. While there might be confusion about support around NFS, I think it's always been clear that image formats cannot be used.

Given that, I don't think this is a candidate for 1.0.


Anthony Liguori


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