Thanks, John. But I don't see an option to specify the # of output files. How does Crush decide how many files to create? Is it only based on file sizes?
On Wed, Jul 31, 2013 at 6:28 AM, John Meagher <john.meag...@gmail.com>wrote: > Here's a great tool for handling exactly that case: > https://github.com/edwardcapriolo/filecrush > > On Wed, Jul 31, 2013 at 2:40 AM, Something Something > <mailinglist...@gmail.com> wrote: > > Each bz2 file after merging is about 50Megs. The reducers take about 9 > > minutes. > > > > Note: 'getmerge' is not an option. There isn't enough disk space to do > a > > getmerge on the local production box. Plus we need a scalable solution > as > > these files will get a lot bigger soon. > > > > On Tue, Jul 30, 2013 at 10:34 PM, Ben Juhn <benjij...@gmail.com> wrote: > > > >> How big are your 50 files? How long are the reducers taking? > >> > >> On Jul 30, 2013, at 10:26 PM, Something Something < > >> mailinglist...@gmail.com> wrote: > >> > >> > Hello, > >> > > >> > One of our pig scripts creates over 500 small part files. To save on > >> > namespace, we need to cut down the # of files, so instead of saving > 500 > >> > small files we need to merge them into 50. We tried the following: > >> > > >> > 1) When we set parallel number to 50, the Pig script takes a long > time - > >> > for obvious reasons. > >> > 2) If we use Hadoop Streaming, it puts some garbage values into the > key > >> > field. > >> > 3) We wrote our own Map Reducer program that reads these 500 small > part > >> > files & uses 50 reducers. Basically, the Mappers simply write the > line & > >> > reducers loop thru values & write them out. We set > >> > job.setOutputKeyClass(NullWritable.class) so that the key is not > written > >> to > >> > the output file. This is performing better than Pig. Actually > Mappers > >> run > >> > very fast, but Reducers take some time to complete, but this approach > >> seems > >> > to be working well. > >> > > >> > Is there a better way to do this? What strategy can you think of to > >> > increase speed of reducers. > >> > > >> > Any help in this regard will be greatly appreciated. Thanks. > >> > >> >
