MDS Diagnostics is Virtual Instruments, OEMed into Cisco MDS switches. Doesn't require TAP and SAN rover which is a huge deal.
We ran a massive array of VI instrumentation across all our VMAX arrays and it's a storage admins dream. We could pin point individual FC frames and IO, correlate with DB IO, determine application performance on the SAN in real time. Cache hits, cache misses, we could identify misconfigured RAID sets just by looking at FC frame statistics. Ridiculously good stuff.
If I understand correctly it's now available in all 16 and 32G MDS switches.