On 10/08/2012 07:51 PM, liguang wrote: > by now, if you want a non-shared migration, you have > to create same files at target as source side, which > seems intorlerable! > > this issue was reported by Reinier Schoof > http://www.redhat.com/archives/libvir-list/2011-December/msg00451.html That's only one instance; the problem itself has been known for much longer, but few enough people use --copy-storage-* flags of migration that no one has bothered to fix it. By the way, the qemu developers have stated that the current implementation of the --copy-storage flags is poorly implemented and may even risk data loss in guests in some cases; they are working on better more efficient ways to do this (such as NBD exports that libvirt would hook up for the duration of the migration), but it will still be a while before all that is ready. Libvirt, of course, will expose the same interface as before, but mapped to the new underlying qemu support. > > These patches try to let migrate --copy-storage-* > work without pre-exist disk image files at target side. > > we may also hope qemu to aware of this issue It's not qemu that has to be made aware, it is libvirt. Remember, with libvirt, you are using sVirt to constrain the set of files that qemu can open. Qemu already knows how to open(O_CREAT) the missing files, but if the files don't already exist, the SELinux prevents that creation. That's why libvirt has to be the one to pre-create the files. -- Eric Blake eblake@xxxxxxxxxx +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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