[ https://issues.apache.org/jira/browse/MAPREDUCE-1838?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ramkumar Vadali updated MAPREDUCE-1838: --------------------------------------- Status: Patch Available (was: Open) Fix Version/s: 0.22.0 Shuffle files to raid before submitting the raid job. > DistRaid map tasks have large variance in running times > ------------------------------------------------------- > > Key: MAPREDUCE-1838 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-1838 > Project: Hadoop Map/Reduce > Issue Type: Improvement > Components: contrib/raid > Affects Versions: 0.20.1 > Reporter: Ramkumar Vadali > Priority: Minor > Fix For: 0.22.0 > > Attachments: MAPREDUCE-1838.patch > > > HDFS RAID uses map-reduce jobs to generate parity files for a set of source > files. Each map task gets a subset of files to operate on. The current code > assigns files by walking through the list of files given in the constructor > of DistRaid > The problem is that the list of files given to the constructor has the order > of (pretty much) the directory listing. When a large number of files is > added, files in that order tend to have the same size. Thus a map task can > end up with large files where as another can end up with small files, > increasing the variance in run times. > We could do smarter assignment by using the file sizes. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.