Mail Archives: opendos/1997/04/26/16:57:09
On 26 Apr 97 at 23:58, Lorier wrote:
> >You mean /more easily done/.
> Better: You don't have to "lock" files, you don't have race conditions and
> hundres of other problems... There is far more that can go wrong if your
> defragging AND allowing write access...
One possible solution is to defrag by rebuilding a copy of the file in a linear
region somewhere, then switching from the old copy to the new one. While a file
is being shifted, block read requests come from the old version, and
block write requests go to the new version, leaving a note to the copier not
to copy the old version of that block from the original contorted file!
The background defrag need not be a perfect defragger. If we can just show that
it will defragment most files without screwing anything up, then we can leave
it chuntering away. A full scale bring-the-system-down defrag tool will only
then be needed if empirical evidence shows that the background one isn't good
enough!
> Adding up a CRC of something that
> changes 1/2 way through is going to make things go BANG I think :)
Now, how would that arise????
> > Better for users if it happens invisibly.
> Umm... Semi-invisibly :) Give the "power users" power to do what they NEED. :)
Yes, I'd agree with that. Invisible in general use, but /findable/ if you wanna
see it!
ABW
--
Alaric B. Williams (alaric AT abwillms DOT demon DOT co DOT uk)
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