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The "Hbase/Troubleshooting" page has been changed by AndrewPurtell. http://wiki.apache.org/hadoop/Hbase/Troubleshooting?action=diff&rev1=31&rev2=32 -------------------------------------------------- 1. [[#13|Problem: Long client pauses under high load; or deadlock if using THBase]] 1. [[#14|Problem: Zookeeper does not seem to work on Amazon EC2]] 1. [[#15|Problem: General operating environment issues -- zookeeper session timeouts, regionservers shutting down, etc.]] + 1. [[#16|Problem: Scanner performance is low]] <<Anchor(1)>> == 1. Problem: Master initializes, but Region Servers do not == @@ -229, +230 @@ == Resolution == * See the [[http://wiki.apache.org/hadoop/ZooKeeper/Troubleshooting ZooKeeper Operating Environment Troubleshooting]] page. It has suggestions and tools for checking disk and networking performance; i.e. the operating environment your zookeeper and hbase are running in. ZooKeeper is the cluster's "canary". It'll be the first to notice issues if any so making sure its happy is the short-cut to a humming cluster. + <<Anchor(16)>> + == 16. Problem: Scanner performance is low == + == Causes == + Default scanner caching (prefetching) is set to 1. The default is low because if a job takes too long processing, a scanner can time out, which causes unhappy jobs/people/emails. See item #10 above. + == Resolution == + * Increase the amount of prefetching on the scanner, to 10, or 100, or 1000, as appropriate for your workload: + [[http://hadoop.apache.org/hbase/docs/r0.20.2/api/org/apache/hadoop/hbase/client/HTable.html#scannerCaching HTable.scannerCaching]] + * This change can be accomplished globally by setting the hbase.client.scanner.caching property in hbase-site.xml to the desired value. +
