I have a Synology DS218+ NAS which has been working very well for the past 7 years.  I mainly use it for my Plex media collection, but also for some local file storage.

It's a bit of a mess though, and when talking to my partner last night about adding her media collection I realised that the drives will be getting a bit old and the risk of failure is rising.  Currently it's just a bunch of disks - an 8TB, a 2TB, and two external HDDs plugged in via USB - not ideal.  It would be good to tidy up this setup, and also provide some redundancy in case of a future drive failure.

Would the simplest solution be to get two 12TB drives and then set them up in the DS218+ as a RAID1?  Or is there a better approach I should be considering?