Hi Harsh Yes, I did set both of these. While not in hbase-site.xml but hdfs-site.xml.
And I have double confirmed that local reads are performed, since there are no Error in datanode logs, and by watching lo network IO. > > If you want HBase to leverage the shortcircuit, the DN config > "dfs.block.local-path-access.user" should be set to the user running HBase > (i.e. > hbase, for example), and the hbase-site.xml should have > "dfs.client.read.shortcircuit" defined in all its RegionServers. Doing this > wrong > could result in performance penalty and some warn-logging, as local reads will > be attempted but will begin to fail. > > On Sat, Feb 16, 2013 at 8:40 AM, Liu, Raymond <raymond....@intel.com> > wrote: > > Hi > > > > I tried to use short circuit read to improve my hbase cluster MR > scan performance. > > > > I have the following setting in hdfs-site.xml > > > > dfs.client.read.shortcircuit set to true > > dfs.block.local-path-access.user set to MR job runner. > > > > The cluster is 1+4 node and each data node have 16cpu/4HDD, > with all hbase table major compact thus all data is local. > > I have hoped that the short circuit read will improve the > performance. > > > > While the test result is that with short circuit read enabled, the > performance actually dropped 10-15%. Say scan a 50G table cost around 100s > instead of 90s. > > > > My hadoop version is 1.1.1, any idea on this? Thx! > > > > Best Regards, > > Raymond Liu > > > > > > > > -- > Harsh J
