I attached an external tonight to my 7232.
For reference, I bought a Vantec NexStar CX enclosure and put a Samsung EcoGreen F4 HD204UI 2TB drive in it.
I THINK it's recognizing the whole 2TB, but I won't be able to tell until I get some substantial recordings on there and do some calculations from the percentage of free space. I went into the diagnostic menu and went down to the drive information page. Here's where I get conflicting info. There are 3 pages on that screen. The first is a summary with a listing of the space available for recordings. On this screen, everything looks good. There's about 1.8TB of space available on the external for recordings which is about right when you take into account format overhead on the drive.
However, on the individual pages following that which shows info on the various drives, it lists the capacity of the external as 1000GB. I'm more inclined to trust the first page though as it's giving free space from a formatted volume and not some dummy rounded number related to the drive. I have a feeling that 1000GB is just the max value that will show up on that screen.