Currently, I have a Supermicro 4U case with seven 8TB hard drives in it, running FreeNAS, Ubuntu on a VM and Pihole on the Ubuntu. It sounds like a jet engine at times (even in the basement) and pulls quite a bit of power. It functions as a storage server for Plex as well.

I recently got a QNAP 8 bay NAS that we pulled from service at work. It had a 2nd gen Core i3 and 2 GB RAM. I pulled it apart and put in a Sandy Bridge Xeon and 8 GB RAM. It has more than enough power for what I need it to do. It currently has seven 4TB drives in a RAID 5 plus an SSD for read caching. I've got it running Pi-hole in a docker and serving Plex. It's quiet and pulls less power.

I want to pull the seven 8TB drives from the Supermicro FreeNAS, pull the seven 4TB drives from the QNAP, and put the 8TBs in the QNAP. Options I've read include:

-Removing a 4TB in the QNAP software, pulling it, hot swapping in an 8TB, letting QNAP format the drive and rebuild the array. Then repeat with the second 4TB drive, and repeat. I get the impression that rebuilding 15-20 TB takes a long, long time. Doing this seven times could take a ridiculous amount of time, although I read that subsequent builds after the first swap are faster. Is this true?

-Buy an external drive (perhaps a WD 10-14 TB drive), back up all of the QNAP data, pull all the 4TB drives, replace with the 8TB drives, start it up, configure as RAID 5, build array. Copy the data back from the external drive? Reinstall the Pi-hole docker.

Would the second option be faster? Is there another method I'm not seeing? My main goal is to use as a file server for each family member, run the QNAP plex app and server movies/TV shows on the LAN, and to run Pi-hole for LAN ad blocking.

I have a Qnap 451 with four 8tb drives.  Upgraded the original 4gb ram to 16gb which Qnap says won't work, but actually does work just fine.

I have a ten tb WD Elements USB 3 outboard drive plugged into the Qnap.  Fast file transfers.

If you're going to be swapping drives this might be the way to go.

Qnap uses a Linux format so you'll lose anything on the drives you're swapping in.