Along the same lines, if its raw volumes you want to test then vdbench is also available (http://sourceforge.net/projects/vdbench/).

Both tools have a good track record and follow a similar pattern, enabling simple replaying of workload sets for consistent evaluation and benchmark/testing. I think the days of the “free tool” being that much of a differentiator are limited, unless this truely is the commiting of code as open source … Asigra need to pony up more than a sales gimmick to compete …