Mixed vdev mirror in ZFS Pool

Looking at drive options again, I purchased a pair of WD Red 4TB Plus drives before Christmas with the plan to get another two, but now out of stock from chosen UK seller.

I’ve got a T340 that can take 8 x 3.5 drives, I wasn’t originally planning on using all bays as it adds to the consumption re power. More so with UK electric pricing at the moment, streamline of running kit I expect on the cars in 2022 with energy prices rising massively.

So I’ve got
4 x 3TB Seagate Contellation Dell drives
3 x WD 3TB Red plus drive in a QNAP atm, migrating data out and will sell the QNAP chassis
2 x WD 4TB Red plus drives, semi wish I hadn’t purchased them, so I may send them back or sell on overclockers.co.uk forums.

I’ve read that it’s not a good idea to mix vdev disk sizes in ZFS pools, so based on the above just use the 3TB drives in one pool and the 4TB drives in another? I am considering replicating data between Pools before replicating it to cloud storage.

I originally got the WD 4TB drives as my thought was to loose the Seagate drives as they’re so damn loud. They’re currently in a 4 x RAIDZ2 setup but can be scrapped if I shuffle data around.

The intended plan at the moment is to end up on TrueNAS Scale for SMB shared data, Plex and a couple of v small VMs. Unifi controller being one so that I can sell my cloud gen2 key for near what I paid for it due to shortages.

You can do individual pools or imbalanced VDEV’s.