On Thu, 5 Oct 2000 22:00:58 +0000, Alain Williams <addw@phcomp.co.uk>
wrote:
>Hi,
>
>I remember when at the University of Cambridge (in England) about 25 years ago
>seeing some work then about the Jackdaw (or was is Jackard) database system
>that had the great feature of being immune to OS crashes, it used a phased
>update mechanism where new blocks were written to disk and the last block
>written was the one that contained the switched pointer, until this last block
>had been written the changes had not been made. Since the write of a disk block
>was atomic the database would never be corrupt.
>
>If someone wants I think that I still have a (paper) copy of the report describing
>this. I can send/fax a copy if wanted.
>
>I don't subscribe to this list, so please reply direct if someone wants it.
>
>(Please don't request a copy just out of curiosity since I don't want to have
>to post/fax copies that won't help resolve this case by showing prior art.)
>
>Cheers
The VM/CMS operating system had a new file system around 1979 or 1980.
It had exactly the same characteristics... writing the new blocks and
then writing a final block which changed the world. The work was
derived from Chris Stephens' work on YMS (Yorktown Monitor System).
Since Chris was part of IBM Research, and since researchers got major
brownie points from patents, I bet that the there are some patents to
be found of interest.
Clearly, the same idea has been rediscovered over and over again. The
VM/CMS case would be a good example of prior art, since it had
thousands of licenses and hundreds of thousands of end users in the
early 1980s.
john alvord
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