One more reason why block storage management doesn't really work on file systems. I'm OK with storing the format, but that just means you fail migration/backup operations with different formats, right?
On Mon, Jun 23, 2014 at 6:07 PM, Trump.Zhang <zhangleiqi...@gmail.com> wrote: > Hi, all: > > Currently, there are several filesystem-based drivers in Cinder, such > as nfs, glusterfs, etc. Multiple format of volume other than "raw" can be > potentially supported in these drivers, such as qcow2, raw, sparse, etc. > > However, Cinder does not store the actual format of volume and suppose > all volumes are "raw" format. It will has or already has several problems > as follows: > > 1. For volume migration, the generic migration implementation in > Cinder uses the "dd" command to copy "src" volume to "dest" volume. If the > src volume is "qcow2" format, instance will not get the right data from > volume after the dest volume attached to instance, because the info > returned from Cinder states that the volume's format is "raw" other than > "qcow2" > 2. For volume backup, the backup driver also supposes that src volumes > are "raw" format, other format will not be supported > > Indeed, glusterfs driver has used "qemu-img info" command to judge the > format of volume. However, as the comment from Duncan in [1] says, this > auto detection method has many possible error / exploit vectors. Because if > the beginning content of a "raw" volume happens to a "qcow2" disk, auto > detection method will judge this volume to be a "qcow2" volume wrongly. > > I proposed that the "format" info should be added to "admin_metadata" > of volumes, and enforce it on all operations, such as create, copy, migrate > and retype. The "format" will be only set / updated for filesystem-based > drivers, other drivers will not contains this metadata and have a default > "raw" format. > > Any advice? > > [1] https://review.openstack.org/#/c/100529/ > > -- > ------------------- > Best Regards > > Trump.Zhang > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > >
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