[ http://issues.apache.org/jira/browse/HADOOP-195?page=comments#action_12379092 ]
Doug Cutting commented on HADOOP-195: ------------------------------------- Everything we're now seeing is consistent with the inter-rack switches being the primary bottleneck. With 188 nodes sharing a 1Gb/s backbone, there's only 600KB/s per node. We're seeing 10 80kB files transferred per second, or 800kB/second, slightly higher, since some files are already on the same rack. Instead of caching temp files in RAM we can instead try to transfer files soon after they are generated and to process them on the remote end soon after they are recieved. That way we can benefit from the kernel's cache, getting performance similar to what we'd see if we cached them ourselves. > transfer map output transfer with http instead of rpc > ----------------------------------------------------- > > Key: HADOOP-195 > URL: http://issues.apache.org/jira/browse/HADOOP-195 > Project: Hadoop > Type: Improvement > Components: mapred > Versions: 0.2 > Reporter: Owen O'Malley > Assignee: Owen O'Malley > Fix For: 0.3 > Attachments: data-transfer-chart.pdf, netstat.log, netstat.xls > > The data transfer of the map output should be transfered via http instead > rpc, because rpc is very slow for this application and the timeout behavior > is suboptimal. (server sends data and client ignores it because it took more > than 10 seconds to be received.) -- 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
