I've experienced computers in the past that did not recognize drives beyond a certain size, tho it has been a while. Cannot help but wonder why they've declared a 10TB max specification and not something larger. Will a 18TB be treated as a 10TB, or simply not recognized at all?
the order goes: file system limitations, then hardware.
So its going to map partitions according to size limits of the file system.
Now if its going to partition an 18TB correctly into its 4 extended partitions it does, I don't know, I would have to look at the whitepaper (if there is one) on this version of their file system to find the max Little-endian inode value.
So it might be limited to a value like 10.894 TB
Which I would try first making two primary partitions to see if it overcomes the filesystem limitations.
Then if that doesn't work, try a primary and extended.
Theoretically, it shouldn't be necessary format them into a file system after partitioning.
Otherwise, I would put the 18TB drive into a NAS enclosure and format it and put two folders on the root directory and set the size to 9TB per nas/cloud mounted folder in the NVR. This puts the 9 TB partition into one file. So you must format the NAS to a file system that can handle that large file like exFAT.
Depending on how the cameras are set up. 20@8mp with 20TB recording is 1 month to 6 weeks worth. with using motion event and constant recording at the same time.
I set the pre and post record of the motion event recording to 1 min. before and 2 min. after. The default settings are too short. Which I recommend this setting on motion event recording.