> Not saying that this is necessarily the best option, but I think reusing > existing > formats and implementation is always a good thing, so it's an idea to > consider.
Yes, I would really like to reuse something. Our current backup software uses 'tar' files, but that is really inefficient. We also analyzed all other available archive formats, but none of them is capable to store sparse files efficiently. And storing data out of order is beyond the scope of existing format.
