What you are looking for is RAID. Specifically RAID 0 would "Stripe" data across the disks. However, it is important to realize that if a singe HD fails, ALL data on all disks is lost. It would be better to setup a RAID 5 (which tolerates 1 disk failure) or RAID 6 (which tolerates 2 failures). However, RAID 5 decreases your usable space by 1 disk (so instead of having 16TB of disk, you have 14). RAID 6 costs you 2 disks, so 12 TB.
The disadvantage of RAID 0 is resilience - do not use it.
The advantage is performance. You write to two disks at once, so its * essentially* 2x as fast.
The disadvantage of RAID 5 or 6 is that its not quite as fast as raid 0 and the disk costs.
The advantage is better performance (compared to no raid) and better resilience.
The disadvantage for all (true) RAID solutions is that is requires hardware, specifically a RAID controller.
There are also software RAID solutions (LVM for Linux, Logical Disk Manager for Windows) if you dont have the hardware. But they will not perform as well as hardware Raid.