When I bought my NAS device, I bought a few Western Digital Green drives to use with it. I wasn’t about to pay the price-premium required for enterprise-class drives! Then, within two weeks, Western Digital released their series of Red drives, which are designed specifically for home and small-office NAS systems. It figures. I bought the Green drives and I was going to use them, damn it!

Except I didn’t. There are a few things that make me uneasy about using the Green drives for my NAS, including that they’re not designed for a 24/7 duty-cycle. So I replaced them with Red drives.

The Green drives sat around until recently when I decided that I’d retire a pair of 1.5 TB Green drives and use two 3.0 TB Green drives in their place. They still had the NAS formatting but I thought that would be simple to remove. I was wrong! No matter what I did, both the PC and the Mac reported a maximum size of 746 GB. I spent half a day troubleshooting the issue. I even wrote to the NAS manufacturer and asked how the heck to undo their device’s formatting. It had to be the formatting because it’s only these drives have this issue, and surely, if my drive dock supported 2 TB drives and no larger, I’d see 2 TB capacity.

Things started to fall into place when I corrected one of them directly to my Windows machine via the internal SATA cable. The PC recognized the drive as being 3 TB in size, and formatted it just fine. So I thought I’d format them that way, and they’d be fine in the dock. It turns out that I never got that far. I did note that I had eliminated the dock as a variable so maybe it was the issue. While the second drive was formatting, I decided to have a look at the Western Digital message board. It couldn’t be the USB dock, but I’d satisfy my curiosity.

As you may have already guessed, it was the dock. Why does it report 764 GB? Older and cheaper drive docks that do not support anything larger than 2 TB are limited to 32 bit logical block addresses. Support for 3 TB drives requires more than 32 bits … so when the computer queries the drive about its maximum size, the dock can’t handle the entire answer and strips the first digit of the number of blocks (in hex). The result, when converted to base-ten is 746.5 GB.

Sure, now it makes sense!

I bought a new hard drive dock and everything works as it should.