We don't expect such drastic slow down.. if b/w you report is the over all throughput.
What are the exact command line you ran? Also how is b/w you report measured? Raghu. Samuel Guo wrote: > Hi all, > > I run the *TestDFSIO* benchmark on a simple cluster of 2 nodes. > The file size is the same in all cases 2GB. > The number of files tried is 1,2,4,8(only write). > The bufferSize is 65536 bytes. > The file replication is 1. > > the results as below: > > files 1 2 4 8 > > write -- Throughout(mb/s) 52.89 52.31 23.06 22.25 > -- Avg IO rate(mb/s) 54.18 53.23 24.03 22.77 > > > read -- Throughout(mb/s) 79.17 60.77 20.15 > -- Avg IO rate(mb/s) 79.18 61.33 22.01 > > > It doesn't seem good. When the number of writes is larger than the size > of the cluster, everything become worse. > > Can anyone explain why everything is getting very slow when the the > number of writes is close to or > larger than the size of the cluster? > > Is there something wrong with my test or the cluster settings? > > Hope for your reply. > > regards, > > Samuel
