Just a side note: If a combiner is used, that usually would be considered as part of the cost of the mapper phase, right?
On Mon, Mar 3, 2008 at 12:17 PM, Amar Kamat <[EMAIL PROTECTED]> wrote: > Currently reducers go through 2 phases > 1) Shuffle phase : copying the map outputs > 2) Reduce phase : Actual reducing > So by starting the reducers we actually start the shuffle phase. Ideally > the shuffle phase should interleaved with the map phase. > Amar > > > On Mon, 3 Mar 2008, Marc Harris wrote: > > > I noticed when reading http://wiki.apache.org/hadoop/HardwareBenchmarks > > the following comment: > > > > "I ran into some odd behavior on Herd2 where if i [ . . . ] the reducers > > don't start until the mappers finish, slowing the job significantly." > >
