WD30EFRX - WD RED - 3.0TB with DUO v.1

1) No. There is no GPT support for Sparc. If you look at the compatibility list (http://www.readynas.com/hcl and the RAIDiator Release Notes (e.g. http://www.readynas.com/RAIDiator_4_1_8_Notes) it is very clear that drives greater than 2TB are not supported.
2) No. It would be recognised as having <1TB in capacity.
3) No

A lot of people (including me) have bought the ReadyNas Duo V1 with the purpose to let the storage grow with time. I cannot regarded as proper product support when larger disks than 2TBn is suddenly not supported. There was no notice of such a limitation when I purchased the ReadyNAS. I was very disappointed when I needed to increase my storage and realized it is not possible! Of course I will not by any more NAS products from Netgear if they choose to abandon their customers in this way.

JohnH wrote:
A lot of people (including me) have bought the ReadyNas Duo V1 with the purpose to let the storage grow with time. I cannot regarded as proper product support when larger disks than 2TBn is suddenly not supported... .

There is nothing sudden about this.

Your Duo (like mine!) is a early 2008 product - introduced over a year before the first 2 TB SATA drive was on the market. It was replaced by the V2 product more than a year ago.

Netgear has had a hardware compatibility list for disk drives for many years, and it never included any 3 TB drive models for the v1 products..

When did you buy?

BTW, if you are maintaining good backups (as you should...) you can rebuild your duo to use 2 1-disk volumes, which will double your storage.