[Beowulf] network filesystem

[Robert Latham]

On Tue, Mar 06, 2007 at 08:17:32AM +0900, Stu Midgley wrote:
> I can't think of any benchmark you care to mention that a single
> lustre OSS/MDS won't outperform NFS.  

Consider an MPI-IO benchmark where all processes write to different
regions of a file.  This workload is common in scientific
applications, say when all processes need to write an HDF5 element to
a datafile.

Run that benchmark with one processor and you will get great
performance out of Lustre.  Lustre does an excellent job of caching
data amd making single-processor I/O go really really fast.

Run that benchmark with two processors, and the clients will spend a
great deal of time revoking each others extent-based locks and
expiring entries from their caches.  Performance will take a
significant hit, but will increase as you add more processes.

I don't mean to come across as a Lustre hater.  I'm just trying to
keep the discussion honest:  the discussion of the "right" file system
for an application is hard, and lots of factors come into play.

==rob

-- 
Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Lab, IL USA                 B29D F333 664A 4280 315B