Tune JVM garbage collection in RegionServers

You can tune garbage collection in HBase RegionServers for stability, because a RegionServer cannot utilize a very large heap due to the cost of garbage collection. Administrators should specify no more than 24 GB for one RegionServer.

1. Specify the following configurations in the HBASE_REGIONSERVER_OPTS configuration option in the /conf/hbase-env.sh.

   -XX:+UseConcMarkSweepGC
   -Xmn2500m (depends on MAX HEAP SIZE, but should not be less than 1g and more than 4g)
   -XX:PermSize=128m 
   -XX:MaxPermSize=128m 
   -XX:SurvivorRatio=4 
   -XX:CMSInitiatingOccupancyFraction=50 
   -XX:+UseCMSInitiatingOccupancyOnly 
   -XX:ErrorFile=/var/log/hbase/hs_err_pid%p.log 
   -XX:+PrintGCDetails
   -XX:+PrintGCDateStamps

2. Ensure that the block cache size and the MemStore size combined do not significantly exceed 0.5*MAX_HEAP, which is defined in the HBASE_HEAP_SIZE configuration option of the /conf/hbase-env.sh file.