I have never added more than 2TB, but this device has never failed no matter what size disk I have added (I have used left over drives of all types). I would look at the other responses though as this is a hard disk housing and is pretty basic but very useful if you have lots of disks laying around like me.

If I was to attempt to add 20TB (x 4) I would definitely look at adding a NAS that has a bit more intelligence / features / flexibility.

There is no space limitation.

According to https://www.fantec.de/produkte..., Araminimichael is absolutely right.
Remember: It is a hard disk enclosure and NOT a NAS.

The manufacturer's website states the supported capacity as "currently unlimited", so yes, the 20 TB hard drives in numbers of 4 should work. Remember that there is no built-in Raid on this model
The manufacturer's website indicates on supported capacity "currently unlimited" so yes, the 20tb disks in number of 4 should work. Remember that there is no built-in raid on this model