On Thu, 2011-09-15 at 14:58 +0200, Paolo Bonzini wrote: > On 09/15/2011 02:34 PM, Orit Wasserman wrote: > >> > Then you need an iSCSI*target* that understands qcow2, like qemu-nbd > >> > but for iSCSI... that's exactly the thing you were worried about > >> > implementing. > > > > Not really , this is just part of the target configuration. > > For each file in the chain we create a lun in the target that is backed > > by the file and we number the luns in chronological order (base is lun > > 1) . you can look at a tgtd configuration here > > http://wiki.qemu.org/Features/LiveBlockMigration#Example_single_base_master_image. > > That's surely a weird way to use iSCSI. :) :) > It's clever, but I would call that shared storage, since you need to > share the details of the snapshot chain between the source and > destination, down to the file names. We need a more precise nomenclature. We store the parent base image inside the image (relative path). We can reverse engineer it in the destination , start at the highest lun ,read it's parent name , create a symbolic link to the parent (previous lun) and so on ...
Orit > Paolo
