So we still do not know if 3TB drives will format in a TwinStore.
We do now

I have just replaced a pair of 2TB Seagates with pair of 3TB Seagates
ST33000651AS Barracuda XT 7200RPM SATA (6GB/s, 64MB Cache) in my TwinStore (RM) using the documented standard method:
- Power-down TwinStore (front press button)
- Removed old 2TB drives
- Fit new 3TB drives
- Power-up TwinStore (front press button)
After about 30 seconds (the boot time) the TwinStore started the familiar 10 second interval drive formatting beep. The beeps continued for circa 8 minutes then the TwinStore made the �fancy multi toned� format / initialising complete beep.
Once completed the TwinStore was listed as having 6TB Media fitted and the C15 reported it as have 2.953507 TB of available free storage space (With the C15�s internal storage disabled).
I have ripped a CD on to the 3TBs which as you would expect ripped and played just fine.
Next up the marathon task of restoring almost all my albums back on to it!
Regards,
Carl
PS I did consider the Seagate Constellation ES.2
ST33000650NS enterprise class drives but but they are currently twice the price of the Barracuda XT!