I don't want to scare you, but you should know that the Seagate 4TB drives have a very high failure rate (upwards of 20-30% failure rate):
https://www.backblaze.com/blog/hard-drive-failure-rates-q3-2017/
Even the DM000 model has a failure rate of 2-3.5%, which is still very high. Interestingly enough, the HGST hard drives are very reliable.
This has been a known problem in the industry when the hard drive manufacturers started pushing out hard drives in excess of 1TB (such as 2TB, 4TB, etc.). The 1TB has been the largest drive that still retained the reliability of the older drives. Obviously, this was not a well published fact as vendors are still pushing larger drives and consumers just want bigger and bigger as time goes along.
If you study this chart, make sure to look at the "drive count" column. Even though Toshiba may appear to have a 0% failure rate, 45 drives is not a good enough sampling for this.