[PVFS2-developers] PVFS2 and data redundancy
rross at mcs.anl.gov
Fri Jun 25 09:16:59 EDT 2004
There is some work going on at Clemson looking into RAID-1 style
redundancy in PVFS2, and that design is shaping up fairly nicely. There
is also some work going on in conjunction with NWU that is looking at
RAID-5, but I would say that work is a little more preliminary at this
Both are relatively difficult problems. The RAID-1 style work will rely
on inter-server communication that is being developed now as well; that
will help quite a bit.
There has also been some work in using dual-attached storage and commodity
failover software to provide node failure tolerance; we've worked out many
of the details of this here on some hardware that Dell was nice enough to
Both the first and the third approaches address metadata redundancy as
well, while the second does not. The third approach is pretty much ready
to go now. I would expect the first approach to mature more quickly than
the second based on design complexity, but I wouldn't want to guess at
when exactly it will be ready for production use.
Of course, the seemingly simplest solution would be to just add a locking
component to PVFS2, make everything work in terms of blocks, and handle
parity writes on the client side. But then you have to make sure that the
locking component is very reliable and you really need to journal changes
on clients in case they fail mid-way through an operation. And of course
your performance drops like crazy for many common parallel write patterns
in this case. It would, however, be an interesting data point to have.
Hope this helps,
On Thu, 24 Jun 2004, Bruce Schwartz wrote:
> I noticed some discussion a while back (2002) about about adding
> RAID-1 and/or RAID-5 style redundancy to PVFS. Has any design or
> further discussion occurred since then on that topic? If not, would
> anyone hazard a guess a to how difficult that would be to add to the
> current PVFS2 codebase?
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