On Tuesday January 17, [EMAIL PROTECTED] wrote:
> Neil Brown wrote:
> > In general, I think increasing the connection between the filesystem
> > and the volume manager/virtual storage is a good idea. Finding the
> > right balance is not going to be trivial. ZFS has taken one very
> > interesting approach. There are others.
> >
> Just out of curiosity... When you say there are others, are you then
> refering to existing solutions or just saying other approaches will be
> developed in the future?
There was a paper given at the USENIX FAST conference
http://www.cs.wisc.edu/adsl/Publications/fast05-journal-guided.pdf
which discussed modifications to ext3 so that after a crash, it would
tell the underlying raid which blocks might have been undergoing a
'write' at the time of the crash, so that raid5 could resync just
those stripes. This reduces the resync time much more efficiently
that write-intent logging does.
I have had a project underway for some time (about half a day a week
at the moment) to create a file system which is raid-friendly. When
configured on a raid5, it will always write a full stripe at a time,
and never over-write live data. This means that there is no need to
pre-read parity or data, and it completely removes the "write hole".
NeilBrown
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