Re: [Qemu-devel] [PATCH 1/5] RFC: Efficient VM backup for qemu (v1)

[Dietmar Maurer]

> > Did you look at the VMDK "Stream-Optimized Compressed" subformat?
> 
> We've gone down several sub-threads discussing whether VMDK is suitable.
> I want to summarize why this is a good approach:
> 
> The VMDK format already allows for out-of-order data and is supported by
> existing tools - this is very important for backups where people are
> (rightfully) paranoid about putting their backups in an obscure format.  They
> want to be able to access their data years later, whether your tool is still
> around or not.

The VMDK format has strong disadvantages:

- unclear License (the spec links to patents)
- they use a very slow compression algorithm (deflate), which makes it unusable 
for backup