I wanted to rearrange disks on my tower, and looked up tips on the forums. Similar threads from 2017 (referring to v6.2.x) have advised that a new configuration may be needed, and parity 2 may need to be rebuilt. 

I rearranged disks and booted up to v. 6.4.0, to see that the array had already started and disks were detected automatically. The disk identifiers (sda, sdb, etc) have changed, but it would seem that unraid now pairs the parity and data disks to their serial numbers automatically, without having to create a new config or rebuilding Parity 2.

 

Just wanted to share this with fellow users for future reference. 

Disk assignment by serial number was introduced since unRAID v5.

 

Starting from unRAID 6.2 dual parity was introduced and when using dual parity it is mandatory that disk assignments stay the same (e.g. disk1 remains disk1) otherwise parity2 is invalidated. The first parity disk works independent from disk order.

 

Physical slot rearrangement is not tied to logical slots in any way. The only possible issue would be if you moved a disk to a controller that didn't pass the drive identification string (model and serial) to unraid in the same form. It's the same degree of freedom that allows you to move all your disks to a totally new system and have unraid bring up the basic array without any hiccups.

 

If you wish to rearrange logical slots you must use the new config tool and rebuild parity 2 as discussed.

 

Your title is ambiguous whether you mean logical assignment or physical assignment. You apparently wanted to do physical rearranging and found answers dealing with logical assignments.