Full capacity of MD3600i with NX3610i

Hello;

We have used a storage system, configured with 1 NX3610i controller and 1 MD3600i DAS device, so far.

It looks like that MD3600i holds 4TB disk fitted in full 12 drive bays with RAID 6 setup.

So I assume that it could give us around 40TB capacity.

However, in the FluidFS system, it gives us only 20TB capacity with 2 nodes 10TB LUNs.

I am wondering how to check up a physical disk status and RAID setup in MD3600i system.

Whenever I connect to web-based PowerVault NAS manager(Version 2.0.4700) via management VIPs of our system, it only shows current nodes and LUNs only.

And if we couldn't figure out the capacity issue, we're going to add more MD devices to increase a capacity.

I found that NX3610i can connect two MD3600i devices.

I am wondering that NX3610i can hook up with a newer MD38xxi series device instead of MD3600i?

Is it better to buy an MD1200 to attach to MD3600i in order to expand the capacity?

Thanks!