Depending on your meaning of “simple concept” you could have a look at Datacore software, I would avoid SAN Melody, but SAN Symphony may meet your requirement. This is a software application, which runs on a windows-based server infrastructure, and provides a level of storage virtualisation. You can present volumes from multiple arrays and have the usual virtualisation benefits. We’ve found it useful to aid migrations.
Moving from that IBM SVC is good for the mid-enterprise space, if you are looking at high-enterprise I’d go for HDS USP every time, it’s rock solid, but with a price point to match