Redundant hot-swap power supplies. The 610 has a single power supply, while the 810 runs dual power supplies so one can fail without taking the appliance offline, on top of the hot-swap RAID both models share.

Up to 5,000 concurrent users at up to 750 Mbps of throughput, roughly double the 610's ceiling. It's sized for a large enterprise or multi-building campus.

Yes. Full SSL inspection is standard from the 410 up, and the 810 is built to run it at enterprise scale without the appliance becoming the bottleneck on your network.

It's a 2U Fullsize appliance, larger than the 1U chassis used by the 310 through 610, which is what makes room for the second power supply and the higher-capacity components at this tier.

Yes, as a subscription add-on across the whole Web Security Gateway line. It runs suspicious files through full system emulation before they reach your network and checks them against Barracuda's global threat intelligence.