[ http://issues.apache.org/jira/browse/HADOOP-445?page=comments#action_12427950 ] Doug Cutting commented on HADOOP-445: -------------------------------------
> What was the performance difference you saw after the patch? I think the performance was about the same, mostly things just became more reliable, since the longer-lived connections caused lots more timeouts. > Parallel data/socket writing for DFSOutputStream > ------------------------------------------------ > > Key: HADOOP-445 > URL: http://issues.apache.org/jira/browse/HADOOP-445 > Project: Hadoop > Issue Type: Improvement > Affects Versions: 0.5.0 > Reporter: Benjamin Reed > Attachments: fastClientWrite.patch > > > Currently, as DFS clients output blocks they write the entire block to disk > before starting to transmit to the datanode. By writing to disk the client is > able to retry a block write if the datanode files in the middle of a block > transfer. Writing to disk and then to the datanode adds latency. Hopefully, > the common case is that block transfers to datanodes are successful. This > patch writes to the datanode and the disk in parallel. If the write to the > datanode fails, it falls back to current behavior. > In my tests of transmits of 237M and 946M datasets using -copyFromLocal I'm > seeing a 20-25% improvement in throughput. -- 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
