more nodes means more IO on read on mapper step If you use combiners you might need to send only small amount of data over network to reducers
Alexander On Tue, Dec 13, 2011 at 12:45 PM, real great.. <greatness.hardn...@gmail.com > wrote: > more cores might help in hadoop environments as there would be more data > locality. > your thoughts? > > On Tue, Dec 13, 2011 at 11:11 PM, Brad Sarsfield <b...@bing.com> wrote: > > > Praveenesh, > > > > Your question is not naïve; in fact, optimal hardware design can > > ultimately be a very difficult question to answer on what would be > > "better". If you made me pick one without much information I'd go for > more > > machines. But... > > > > It all depends; and there is no right answer.... :) > > > > More machines > > +May run your workload faster > > +Will give you a higher degree of reliability protection from node > > / hardware / hard drive failure. > > +More aggregate IO capabilities > > - capex / opex may be higher than allocating more cores > > More cores > > +May run your workload faster > > +More cores may allow for more tasks to run on the same machine > > +More cores/tasks may reduce network contention and increase > > increasing task to task data flow performance. > > > > Notice "May run your workload faster" is in both; as it can be very > > workload dependant. > > > > My Experience: > > I did a recent experiment and found that given the same number of cores > > (64) with the exact same network / machine configuration; > > A: I had 8 machines with 8 cores > > B: I had 28 machines with 2 cores (and 1x8 core head node) > > > > B was able to outperform A by 2x using teragen and terasort. These > > machines were running in a virtualized environment; where some of the IO > > capabilities behind the scenes were being regulated to 400Mbps per node > > when running in the 2 core configuration vs 1Gbps on the 8 core. So I > > would expect the non-throttled scenario to work even better. > > > > ~Brad > > > > > > -----Original Message----- > > From: praveenesh kumar [mailto:praveen...@gmail.com] > > Sent: Monday, December 12, 2011 8:51 PM > > To: common-user@hadoop.apache.org > > Subject: More cores Vs More Nodes ? > > > > Hey Guys, > > > > So I have a very naive question in my mind regarding Hadoop cluster > nodes ? > > > > more cores or more nodes - Shall I spend money on going from 2-4 core > > machines, or spend money on buying more nodes less core eg. say 2 > machines > > of 2 cores for example? > > > > Thanks, > > Praveenesh > > > > > > > -- > Regards, > R.V. >
