zip (was: Re: Disk archival techniques)

[Paul Koning]

>>>>> "Jim" == Jim Leonard <trixter at oldskool.org> writes:

 Jim> Jules Richardson wrote:
 >>> The problem I see with zip is the single table of contents at the
 >>> end.  Did you try corrupting THAT with a hex editor?
 >> Ahh, no not at the time. I've just tried it now though and it
 >> seems remarkably good at recovering from corruption in the TOC
 >> area. Actually, looking at the zip file it appears to have
 >> something resembling a file header before each file in the archive
 >> as well as the TOC at the end.

 Jim> As long as we're talking about fault-tolerant archives, neither
 Jim> TAR nor ZIP are acceptable.  For years I've used RAR (WinRAR for
 Jim> windows, RAR and RAR32 for DOS) which has "recovery record"
 Jim> support (parity info). ...

If you want fault tolerance, it may be a good idea to learn the topic
of "erasure codes" -- a general concept for way to split data into N+K
pieces such that you can reconstruct the data from any N pieces (for N
and K chosen to be whatever you wish).

VMS also implemented the XOR thing you mentioned in the BACKUP
utility (as did RSTS, of course -- since it supports the same
format). 

	 paul