What 4 bay TB JBOD for new imac?

I don't know that I can give you a definitive answer but I have two Promise Pegasus R4 TB RAID's daisy chained together using TB to my MacMini. Each contains 4x 2TB drives and they have worked flawlessly since the day they were attached over a year ago.
Some people say the fans are too loud and they are problematic but I can only tell you my experience. Fans are audible but not intrusive and as for operation. They are on 24/7 and I have never had a day's problem. I had DROBO pro before (iSCSI not TB) and that was terrible. I had to reset the drive every time I came to the computer because it lost connection even if the mac went into sleep. The R4 on the other hand - brilliant.

Hope this is of some help.

 

Just curious what version of Raid are you running, and what sort of real-world read/write speeds are you getting with that? I've looked at them, but for me, the cost is prohibitive.

 

The boot issue is that you cannot boot from it due to the need for a driver at boot time.