On Wed, Jun 06, 2018 at 12:48:17PM +0100, Daniel P. Berrangé wrote: > On Wed, Jun 06, 2018 at 12:42:28PM +0100, Richard W.M. Jones wrote: > > On Wed, Jun 06, 2018 at 12:14:07PM +0100, Dr. David Alan Gilbert wrote: > > > The problem with having a separate file is that you either have to copy > > > it around with the image or have an archive. If you have an archive > > > you have to have an unpacking step which then copies, potentially a lot > > > of data taking some reasonable amount of time. Storing a simple bit > > > of data with the image avoids that. > > > > This isn't really true. For OVA (ie. tar) we don't unpack them. > > Adding file.offset and file.size in qemu's raw driver was crucial to > > that optimization. > > Though that assumes you're only using the qcow2 file in read-only mode. > As soon as you need write access you need to unpack from the OVA so that > the qcow2 file can grow its length when new sectors are allocated.
Sure but you cannot write to an OVA anyway because it contains embedded checksums. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html
