4x4 raid 5 to 3x10 raid 5. Best way to do it?

[njhorn]

Need some advice... I have a 3204t that I’m very happy with. Have 4x4TB red drives in it now in a road 5, but picked up 4 10Tb easystores to shuck today. Only planning on using 3 of the drives right now and going from a 4 drive 12TB to a 3 drive 20TB and keeping the fourth drive external for now. Eventually will add in a fourth drive to expand to 30TB when needed.

Seeing as how I’m using all four slots right now, I can’t just replace drives one by one and then expand the filesystem. I have about 9TB of data so I plan to use the extra 10Tb drive to backup the current array to over USB and then just replace the entire array at once.

How do I move settings/apps/docker containers/OS over to the new array after I do that? I’d like to just backup, replace the drives, copy the data back over, and have everything just work

[njhorn]

One idea I had is to backup to an external, and then fail the current array by putting a single drive in and creating a single volume with it, then copy all the data over to the single volume, pull out rest of old drives, and convert the single volume to a raid 5 adding two more drives. But how do I get the settings and such for the NAS and the docker containers to the new volume/array?