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luoli commented on HDFS-1295: ----------------------------- I think the trade-off is depends on how the hdfs been used. In our case, the High Availability problem is much more important than the cleanup delay because much applications depend on the hdfs to perform service 7 * 24. So I agree with Dhruba that this is a fine tradeoff. > Improve namenode restart times by short-circuiting the first block reports > from datanodes > ----------------------------------------------------------------------------------------- > > Key: HDFS-1295 > URL: https://issues.apache.org/jira/browse/HDFS-1295 > Project: Hadoop HDFS > Issue Type: Improvement > Components: name-node > Reporter: dhruba borthakur > Assignee: dhruba borthakur > Fix For: 0.22.0 > > Attachments: shortCircuitBlockReport_1.txt > > > The namenode restart is dominated by the performance of processing block > reports. On a 2000 node cluster with 90 million blocks, block report > processing takes 30 to 40 minutes. The namenode "diffs" the contents of the > incoming block report with the contents of the blocks map, and then applies > these diffs to the blocksMap, but in reality there is no need to compute the > "diff" because this is the first block report from the datanode. > This code change improves block report processing time by 300%. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.