Start with Understanding Your Performance Requirements
George is on target with his analysis on when to deploy server-side flash versus flash in a networked storage device. When looking at networked storage, the key to making the right SSD/HDD tradeoffs is understanding the workloads that will interact with the storage system. The best approach to characterizing your installed workloads is to leverage a workload analysis and modeling solution from organizations like Load Dynamix. One you have a realistic model of your applications, you can easily gnerate load to test multiple products from different vendors and also evaluate the various SSD/HDD configurations to see what is most cost-effective and affordable for YOUR specific application workloads.