I concur with the NexentaStor suggestion, but since I work for Nexenta I suppose that's expected. Bear in mind no matter whom you go with, big storage (which 200 TB would qualify as, if on the low end) really requires some grasp of your use-case(s) and a discussion with a qualified storage engineer if you don't want to end up with something that is at best over-powered for your needs, and at worst far under-powered for your needs. There's a discussion to be had about what you intend to do with it (all uses), and where in the triangle you sit.
The triangle is the big 3 parts of storage, and the old saying goes (well, there's many variations of it, but here's one):
Capacity, Performance, Redundancy -- pick two.
No matter who you go with (and I always recommend shopping around), talk through your use-case with someone there, and make sure you get a SAN that's suited for your needs (and when in doubt, always err on the side of caution; a slightly over-built SAN is a good problem to have, as opposed to an under-built SAN and the terrors it can bring you).
I'd also suggest that unless you have a compelling reason for it, 1 system holding 200 TB may be a bad place to start. Perhaps go with 4 systems each holding 50 TB, or 2 systems holding 100 TB each, as safer (failure doesn't lead to 100% outage) and higher performance alternatives.