One common question is, is the storage performing properly? One way to tell is to benchmark it.
there are lots of tools to run benchmarks, but you want a tool that will allow you to simulate you production workload as close as possible. This includes read/write mixture, %random vs sequential, block size, cache hit ratio and even wait time. To achieve this, there are a few good tools to use.
IOMeter is an open source tool that provides a lot of flexibility
IORate is a tool by EMC that gives you even more options, including adjusting the cache hit ratio