Index: src/docbkx/book.xml
===================================================================
--- src/docbkx/book.xml (revision 1038359)
+++ src/docbkx/book.xml (working copy)
@@ -299,7 +299,10 @@
in branch-0.20-append to see list of patches involved.
HBase bundles the Apache branch-0.20-append Hadoop.
Replace the Hadoop jar bundled with HBase with that you have
- installed on your cluster to avoid version mismatch issues.
+ installed on your cluster to avoid version mismatch issues;
+ for example, versions of CDH do not have HDFS-724 whereas
+ Hadoops branch-0.20-append branch does have HDFS-724. This
+ patch changes the RPC version because protocol was changed.
Recommended Configuations
+ zookeeper.session.timeout
+ The default timeout is three minutes. This means that if a server crash,
+ it will be three minutes before the Master notices the crash and starts recovery.
+ You might like to tune the timeout down to a minute or even less so the Master
+ notices failures the sooner. Before changing this value, be sure you have
+ your JVM garbage collection configuration under control otherwise, a long
+ garbage collection that lasts beyond the zookeeper session timeout will take out
+ your RegionServer (You might be fine with this -- you probably want recovery to start
+ on the server if a RegionServer has been in GC for a long period of time).
+
+ To change this configuration, edit hbase-site.xml,
+ copy the changed file around the cluster and restart.
+
+ We set this value high to save our having to field noob questions up on the mailing lists asking
+ why a RegionServer went down during a massive import. The usual cause is that their JVM is untuned and
+ they are running into long GC pauses. Our thinking is that
+ while users are getting familiar with HBase, we'd save them having to know all of its
+ intriciacies. Later when they've built some confidence, then they can play
+ with configuration such as this.
+
+
Configuration for large memory machines