Storage and RAID Levels question (pre-sales question)

I am getting ready to buy a DX4000, but have some questions:

Are all the units the same - just different drive configuration?  Or do they have 2-drive bay only and 4-drive bay units too?

If I buy the 4TB and it comes with RAID1, I’m really only getting 2TB of actual storage space.  So if I buy the 16TB unit, I’m really only getting 8TB of space.  True?

Not that I’d do this, but can I change to RAID 0 ever?

Let’s say I buy the 4TB 2x2TB) - later on, an I hot-swap drives out to add 2x3TB or 2x4TB drives?  And if my unit is a 4-bay model, can I do the same?

Thanks

all boxes are 4 bays and you use one drive for “redundancy”

You can purchase with 2 or 4 drives

2 drives is raid 1.  3 or 4 drives is raid 5

So you purchase a 4tb box, you have 2 useable.  add one 2tb drive, it automagicly converts to raid 5 and you have 4tb useable.  If you remove that 3rd drive it does not go back to raid 1, it will keep running and complain a drive is missing.

You must purchace “special” drives to add to the box

16tb would give you 12tb useable

You cannot change the raid levels.  It WILL be raid 1 or 5 depending on how many drives are in it