On Thu, 14 Mar 1996 15:24:17 +0000 (GMT), Alan Cox <alan@cymru.net> said:
>> and the authors are looking at alternatives to sync writes which
>> preserve the metadata consistency (by using either ordered async
>> writes or rollback mechanisms).
> I'm under the impression some of the USL related people have a US software
> patent on ordered async writes. Probably worth someone checking this out.
Yes. Novell obtained such a patent for Unixware. Terry Lambert was
working for them at the time and can supply all the unpleasant
details. Fortunately, Ganger's soft update mechanism is based on
rollbacks, not ordered writes, so is not affected by the patent. Soft
updates are probably the way to go; they don't suffer from the
horrible cyclic dependencies of ordered write implementations.
Cheers,
Stephen.
-- Stephen Tweedie <sct@dcs.ed.ac.uk> Department of Computer Science, Edinburgh University, Scotland.