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Date: Tue, 24 Jun 2014 22:47:09 +0200
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Subject: Re: [Qemu-devel] Live Migration with different block devices
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To: Eric Blake <eblake@redhat.com>, Xiongzi Ge <gexxx132@umn.edu>
Cc: qemu-devel@nongnu.org

Il 24/06/2014 22:41, Eric Blake ha scritto:
>> >
>> > I am trying to do migration with two different block devices in the source
>> > and destination hosts.  For example, in the source the data in /dev/vda
>> > are  'aaaaa'. The guest has a cache. These data are cached.  In the other
>> > host, the data in this device are 'bbbbb'.   If we do migration, I want
>> > the  guest vm recognize this change.  How does qemu deal with the cache
>> > data?  Thanks.
> If you want the guest to see different disk contents, then hotunplug the
> original and hotplug in the new disk.  Migration is NOT supposed to
> change disk contents.  Your problem is independent of migration.

Or if you really do not want to do that, all access to the disk has to 
be done with O_DIRECT in the guest.

Paolo