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Eric Newton commented on ACCUMULO-1083: --------------------------------------- {noformat} shell> config -s tserver.wal.replication=2 {noformat} The setting is for the entire tablet server, not just one table. I don't know if anyone would really want to use a replication factor of one, since it will create a single point of failure. > add concurrency to HDFS write-ahead log > --------------------------------------- > > Key: ACCUMULO-1083 > URL: https://issues.apache.org/jira/browse/ACCUMULO-1083 > Project: Accumulo > Issue Type: Improvement > Components: tserver > Reporter: Adam Fuchs > Fix For: 1.6.0 > > Attachments: walog-performance.jpg > > > When running tablet servers on beefy nodes (lots of disks), the write-ahead > log can be a serious bottleneck. Today we ran a test of 1.5-SNAPSHOT on an > 8-node (plus a master node) cluster in which the nodes had 32 cores and 15 > drives each. Running with write-ahead log off resulted in a >4x performance > improvement sustained over a long period. > I believe the culprit is that the WAL is only using one file at a time per > tablet server, which means HDFS is only appending to one drive (plus > replicas). If we increase the number of concurrent WAL files supported on a > tablet server we could probably drastically improve the performance on > systems with many disks. As it stands, I believe Accumulo is significantly > more optimized for a larger number of smaller nodes (3-4 drives). -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira