My ReadyNAS Pro is currently initializing the 4 1.5TB Seagate disks I dumped into it.

Here are some thoughts on the product...

Build quality: Sub-par for something costing this much. It's basically a small form factor PC case with drive rails. The drive brackets/caddies are flimsy and prone to insertion or removal problems. The slide action/fit of each rail/caddy is different, with a couple on the bottom being quite difficult to slide in and out. They include exactly the amount of screws you will need for 6 drives. Seeing as these are not the same length or head you'd find on typical drive screws, they should have included extras.

The instructions and quick-start guide are the worst I remember seeing for any product from any American company. Terrible.

The Mac OS software looks like crap. They didn't even take the time to make a proper icon. Not of huge importance, but it makes a very bad first impression when laying down over a grand for an empty box. It's shameful.

The web UI is very mid-90's design, though it seems to work. Many items are worded poorly or made overly complicated. Settings possibilities look decent enough though.

The big drawbacks of this product over a Drobo Pro are that it holds two less disks (6 versus 8) and that it can only protect for up to 2 disk failures while the Drobo protects up to 2 SIMULTANEOUS disk failures. Let me explain the difference... In the ReadyNAS, you can have up to two disks fail at any time if so configured. But you must replace those disks in order to gain back any protection at all. In other words, those disks fail but no rebuild is performed until you put in new disks. With the Drobo, the system will start rebuilding each time a disk fails. That means once the rebuild is complete you can have another two disks fail, provided you have enough free space of course. The unit not only dynamically expands, but it can dynamically contract if you have little enough data to do so.

Of course on the flip side, chances are your Drobo Pro will crap out and bork your entire array during the rebuild. But the idea and theory are nice. And of course the ReadyNAS isn't pig-slow like the Drobo and can support multiple simultaneous users effortlessly.

If you monitor your array you shouldn't just let it sit there after a disk failure, so in the real world, the dynamic down-sizing isn't likely to be an issue. But having two more drives bays would be nice. So would not having to use caddys.