what are the best practices for using splunk, and how do you determine storage/sizing
in particular, there is information about storage/sizing here:
http://docs.splunk.com/Documentation/Splunk/latest/Installation/HowHowmuchspaceyouwillneed
I also believe you will find this useful
http://wiki.splunk.com/Community:More_best_practices_and_processes
I believe you are looking for this.