Hello, I'm looking for guidance on best practice when replacing >1 drives with 1 drive. If there is current/relevant documentation for my scenario and I am failing to find it, please link me to the correct document/guide.

I've included diagnostics, but as a brief overview of my array as-is, I've also included this screenshot.

Disks 1-4 are not only very old (average spinning-time of 7.5 years), but were all purchased at the same time, which leads me to believe that if one of them were to fail, there is a high likelihood of another failure during rebuild. I have a new 8TB drive (and another on the way) that I would like to replace the highlighted disks, 1 & 2 with. I cannot find a clear/definitive answer on the practice to do so properly. There's options (seemingly) ranging from taking one out at a time and letting parity rebuild, using Unbalanced to empty disks 1-2, using the New Config tool/utility, or possibly all or even none of these.

I'd also be open to any opinionated ideas on if I should instead be simply adding a 2nd parity drive. None of the array's data is unreplaceable, just painful to do so.

Many thanks in advance to any who are able to assist or have had experience performing similar upgrades.

dd-nas-diagnostics-20251009-1005.zip

I'm doing exactly this at the moment, and my plan is to move all the data off the drive I'm pulling and then swap in the EMPTY new drive by creating a new configuration. Then tell the system the parity is good when I bring it online.