[ http://issues.apache.org/jira/browse/HADOOP-93?page=comments#action_12370887 ]
Doug Cutting commented on HADOOP-93: ------------------------------------ With such big input files the default logic should split things into dfs block-sized splits. Smaller splits should only be used if this would result in fewer than mapred.map.tasks splits. What value do you have for mapred.map.tasks in your mapred-default.xml? Let's make sure that is working before we add a new min.split.size feature. I don't oppose the feature, but it should be generating 356*30G/32M splits, not 356*30G/2K splits as you claim. That's still a lot of splits. If it is too many then we should add the feature you're adding. Note that, as a workaround, it is also easy to implement this w/o patching by defining an InputFormat that subclasses InputFormatBase and specifies a different minSplitSize. But making that a long is a good idea. So, in summary, can you please confirm that the actual number of splits that you object to is 356*30G/32M splits, not 356*30G/2K? Thanks. > allow minimum split size configurable > ------------------------------------- > > Key: HADOOP-93 > URL: http://issues.apache.org/jira/browse/HADOOP-93 > Project: Hadoop > Type: Bug > Reporter: Hairong Kuang > Attachments: hadoop-93.fix > > The current default split size is the size of a block (32M) and a > SequenceFile sets it to be SequenceFile.SYNC_INTERVAL(2K). We currently have > a Map/Reduce application working on crawled docuements. Its input data > consists of 356 sequence files, each of which is of a size around 30G. A > jobtracker takes forever to launch the job because it needs to generate > 356*30G/2K map tasks! > The proposed solution is to let the minimum split size configurable so that > the programmer can control the number of tasks to generate. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
