Hi Neutron - Check out a very similar thread from about a year ago : http://www.beowulf-underground.org/pipermail/pvfs2-users/2009-April/002770.html
Im not sure if we found out what was actually causing the performance differences.. but its probably a start to look into. Best, Kyle Schochenmaier On Fri, Apr 30, 2010 at 7:08 PM, neutron <[email protected]> wrote: > Hi all, > > I have a pvfs2-2.8.1 with 4 DS. "BMIModules" is set to "bmi_ib". I > use simple-tripe mode with stipe-size =1MB. > > 8 client nodes mount pvfs2, and I use iozone to measure the write > throughput, with each client node runs one iozone process. > Each process writes 1GB file with block size = 4MB. > > I got the following results: > > Test running: > > Children see throughput for 8 initial writers = 98513.53 KB/sec > Min throughput per process = 11406.64 KB/sec > Max throughput per process = 12642.13 KB/sec > Avg throughput per process = 12314.19 KB/sec > Min xfer = 946176.00 KB > CPU Utilization: Wall time 86.492 CPU time 6.355 CPU > utilization 7.35 % > > > Test running: > Children see throughput for 8 rewriters = 2499467.09 KB/sec > Min throughput per process = 289479.62 KB/sec > Max throughput per process = 321507.38 KB/sec > Avg throughput per process = 312433.39 KB/sec > Min xfer = 946176.00 KB > CPU utilization: Wall time 3.272 CPU time 5.990 CPU > utilization 183.08 % > > > We can see the "initial write" gets very low throughput, while the > "rewrite" gives very high bandwidth. > My questions are: > 1. Why 8 client nodes as a whole get low throughput? > 2. Why at "rewrite" phase, the write bandwidth boosts ? > > > > -Neutron > _______________________________________________ > Pvfs2-users mailing list > [email protected] > http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users > _______________________________________________ Pvfs2-users mailing list [email protected] http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users
