Frontview formats a FOUR tb external drive as a TWO tb ext3!

So I thought I'd found a reasonably priced high-capacity external hard drive for backing up my ReadyNAS:

Western Digital My Book Studio Edition II - 4 TB (Mac-formatted out of the box)
http://www.wdc.com/en/products/Products.asp?DriveID=621

Having read on the forums that Readynas doesn't talk to HFS USB drives, and that FAT32 supports maximum 2TB partitions, I used Frontview to format it to ext3 (Wikipedia implies 4TB ext3 partitions are OK).

Here's what FrontView gave me after successful reformat to ext3: Volumes/USB Shares:

1 WD My Book [Partition 1] 1671 GB 1671 GB EXT3 480

I was hoping this was some Frontview issue, but alas - I got the error message trying to back up 2.7TB of data saying backup interrupted because the destination drive is full.

When I later connected the drive to My Mac, the disk's contents was unreadable as expected, but the Disk Utility lists the drive as having 3.6TB capacity, and the WD RAID Manager software now still shows it's in RAID0 with 3 726 GB capacity (this is AFTER ext3 formatting) ), so I am pretty sure it comes in 4TB RAID0 mode from the factory and not in the 2TB mirror mode.

The $500 question is - does the ext3 filesystem allow 4TB partitions? If yes, does ReadyNAS's built-in disk format utility limit the size to 2TB? If yes, will it be fixed?

Correction: it's the $250 question - I can stil use 2TB out of four :)

Thanks.

Here's my SETUP SUMMARY

* READYNAS PRO Pioneer Edition 5 x 1.5TB Seagate Barracudas running RAIDiator 4.2.5
+ Fast USB writes enabed

* MacOS 10.5.8
* Western Digital My Book Studio Edition II - 4 TB

+ connected to a USB port in the back

+ formatted to ext3 using Frontview, the main log saying "Successfully created EXT3 file system on the USB device. [USB_HDD_1]"

+ backed up to using Frontview backup tools, two shares totalling 2.7TB, one backed up fine, the other failed giving numerous error messages in the backup log in the following format:

"cp: cannot create regular file `/USB_HDD_1/DVD/Movies/*FILENAMES HERE*': Read-only file system"
"cp: cannot create directory `/USB_HDD_1/DVD/Movies/*FILENAMES HERE*': No such file or directory"
+ the main log says "Sat Aug 29 13:59:02 MSD 2009 Произошла ошибка копирования данных из источника ==> /USB_HDD_1/ из-за недостатка места на диске. [Задание 002]" - Russian for "backup error ... due to lack of space on the disk"