Increasing Read Times with Accumulo

A few weeks ago I wanted to increase performance of the Accumulo 1.5 so that scanning through large tables for information would happen a faster rate. I think I was getting around 200,000 entries per second prior to this performance modification.  I was able to increase the speed to what is now almost 3,000,000 entries per second with the following steps.

Stop Accumulo
I am able to stop the entire cluster by running the stop-all.sh script inside the Accumulo home folder's "bin" directory.

Increase JVM Heap Space to accommodate larger Index Cache 
The Tablet server heap space is defined in the file "accumulo-env.sh" located in the Accumulo home folder's "conf" directory.  Inside this folder you can see the settings for tablet server Xmx and Xms at the bottom defined as an environment variable, "$ACCUMULO_TSERVER_OPTS".  Depending on how much memory is available you will want to increase this value to support the increase we will make to the index cache next.  Here is my setting:
ACCUMULO_TSERVER_OPTS="${POLICY} -Xmx1024m -Xms512m "

Increase Index Cache
In the Accumulo home folder's "conf" directory, you should also see a file called "accumulo-site.xml".  Here you can define properties for the Accumulo cluster.  I have set the cache.index.size to 512M:

 
    tserver.cache.index.size
    512M
 

I have not had any issues with tablet server memory yet, so I believe this is a good fix.  Please provide feedback and comments below.

There are various other performance tweaks as well.  Such as NOT using LVM with CentOS/RHEL, and ensuring any virtual machines in the cluster are running with "Independent Disk Mode" so writes are flushed straight to disk.