Hi Roger - Depending on your setup I would expect that writes would be faster than reads simply because you'll have a lot of server-side caching of the data on writes and those might be sent out to disk before your reading tests. Are you doing any tests that you're positive you're exceeding the caches on the servers for writes with? (writing out 100GB+ files for example) ?
There are some pvfs2 tunables that will force disk flushes on every write in the config file, which would help to see if this really is just caching, Im not sure what the flag is off the top of my head though. I think it is setting troveio to 'directio' : - directio. This uses a direct I/O implementation to perform I/O operations to datafiles. This method may give significant performance improvement if PVFS servers are running over shared storage, especially for large I/O accesses. For local storage, including RAID setups, the alt-aio method is recommended. Also keep in mind that NFS can do client side read caching so reads are almost always going to be faster than writes. Cheers, ~Kyle Kyle Schochenmaier On Mon, Jul 1, 2013 at 3:49 PM, Moye,Roger V <[email protected]> wrote: > We are currently testing a new PVFS2 setup at our facility. The servers > are running on RHEL 6 using XFS as the underlying filesystem. We are using > four PVFS servers. Performance is beating NFS, which is what we wanted and > expected.**** > > ** ** > > While running some simple I/O tests today I discovered that writes are > about 30% faster than reads. I expected reads to be faster. Further, > when I tried the same I/O tests to the local disk of the client, and to an > NFS server running on the same server hardware, I found that reads were > indeed faster than writes by 3:1.**** > > ** ** > > Is it expected that reads would be slower on PVFS? Is there something I > need to tune?**** > > ** ** > > Thanks in advance!**** > > -Roger Moye**** > > ** ** > > -----------------------------------------------------------**** > > Roger V. Moye**** > > Systems Analyst III**** > > XSEDE Campus Champion**** > > University of Texas - MD Anderson Cancer Center**** > > Division of Quantitative Sciences**** > > Pickens Academic Tower - FCT4.6109**** > > Houston, Texas**** > > (713) 792-2134**** > > -----------------------------------------------------------**** > > ** ** > > _______________________________________________ > Pvfs2-users mailing list > [email protected] > http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users > >
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