On Fri, Jan 22, 2010 at 3:57 AM, stephen mulcahy <[email protected]> wrote: > Hi, > > I've been running some tests on some new hardware we have acquired. > > As a baseline, I ran the Hadoop sort[1] with 10GB and 100GB of data. As an > experiment, I ran it on 4 systems (1 configured as master+slave and 3 as > slaves) - first with an MTU of 1500 and then with an MTU of 9000. > > I was somewhat surprised at the results of enabling Jumbo frames - it > resulted in a slowdown. In the case of the write operations, the slow down > was about 5%. In the case of 10GB sort, the slowdown was around 6% and in > the case of the 100GB sort, the slowdown was nearly 20%.
Are normal (non-hadoop) file transfers faster between the same hosts with jumbo frames enabled? ie have your ruled out host/configuration issues? Often a slowdown with jumbo frames means some part of the network can't support them and the packets are getting fragmented as a result. You can a tool like tshark to see if that's happening. Thanks, Eli
