Best duplication option for 3 drives

[acdsosys]

Currently have 2x 1Tb drives as a pool and 2x 3Tb drives as a 'manual backup' pool for the 2x 1Tb data plus my dashcam footage. All data is backed up to my Qnap nas as well. 

I have each pool set for 2x duplication at pool level.

I'm about to remove all 4 of those (Barracuda) and go with 3x 4Tb (Ironwolf) drives.

My question is, if I stick with 2x duplication will I get more storage as files are only split across any 2 drives or would I be better going with 3x duplication so all drives get the same data?

Like I said, all data is weekly backed up to a Qnap Nas (which is also backed up to a 2nd Qnap Nas) and a new external USB 8Tb Seagate drive (yes, I learnt the hard way a while ago about having backups!)

 

[OrozarBE]

Considering you have a backup I would suggest just to use 2x. Even that seems unnecessary but I understand your reasons. With 3 disks 2x is good enough to rebuild if a disk should fail. There is no reason to have the exact same data on all 3 disks with drivepool imo.