Re: [libvirt-users] libvirt live migration, qcow2 image, nbd server

On 02/12/2015 07:41 PM, Edward Young wrote: > Hi all, > > > When I live migrate a vm using > > "migrate --live --copy-storage-all mig-vm qemu+ssh://192.168.1.3/system > tcp://192.168.1.3" > > > I got the following error > > > WARNING: Image format was not specified for > 'nbd://node2:49155/drive-virtio-disk0' and probing guessed raw. > > 258 Automatically detecting the format is dangerous for raw > images, write operations on block 0 will be restricted. > > 259 Specify the 'raw' format explicitly to remove the restrictions. > Was that error printed by the source or the destination qemu? It may be a bug in libvirt for not explicitly requesting raw (we DO want the NBD server to be raw, but need to be explicit so as to avoid unsafe probing).

> >>From the error itself, I can tell that nbd server treat this image as raw, > rather than qcow2. My platform is libvirt+qemu. the image type of this vm > is indeed qcow2. I do not know how to let nbd know this image format. Just because the underlying file on the disk is qcow2 does not impact what the NBD is serving - the NBD connection MUST be raw, unless you have a funky situation with a qcow2 file whose contents are also a nested qcow2 encoding of data.

-- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org