Yes you need 4 disks at a minimum, but no, the loss of a single disk should not take the shebang down. Not even for raid 0+1. And certainly not for raid 1+0.

With only 2 drives, you really can't do raid 0+1 or raid 1+0, unless you take the view that each drive counts as a striped array with a 72 GB wide stripe. So then you simply mirror the drives and then the loss of one drive is still not a system killer.