Furthermore, when you buy a 1.5TB drive, the actual capacity is 1,500,000,000,000 bytes. However in OS it consider 1024 Bytes as 1KB, 1024KB as 1MB, and so on. So OS will recognize your 1.5TB drive as 1,500,000,000,000/1024/1024/1024/1024=1.364TB.
Correct me if i am terribly wrong, but in a RAID5, three of your four disks will be used as "use-capacity" and one whole disk will save the parity, so actually, if you see 3.9TB free space, there's somethin wrong with your setup, you should see 3.5TB storage, as one quarter of the total technical capacity will be "lost" to parity.
I am going to install three 1.5TB drives in RAID5 today, hope Intel's specs are right and i can map a max of 4TB storage, i am afraid they actually meant 4TB of total disk space...
Forget my last post, too bad i had no chance to edit it to correct my math.
Anyway; i have four 1.5TB (1.500.000.000.000 byte) disks (Samsung HD154UI) connected to the SS-4200 and it's running in RAID5 mode.
Overall Capacity is displayed as "4113" GB which quite exactly hits the sumemd capacity of the formatted drives.