Just for testimony.
This morning I wont enableing fair scheduler on my MR1 cluster implementing
HDFS + MR1 + HBase
I use Snappy compression for some of my Htables.
According to http://archive.cloudera.com/cdh4/cdh/4/mr1/fair_scheduler.html
you just have to add the proper HADOOP_CLASSPATH in hadoop-env.sh in
DON'T DO THAT if you use Snappy compression in HBase (at least).
After that restarting HBase regionserver, then it could not load the Snappy
codec and could not open HTables using Snappy compression any more ruining
our log files.
add the HADOOP_CLASSPATH setting in /etc/default/hadoop-0.20 instead ...
this is only used by jobtracker & tasktracker and not HBase.