I run a TrueNAS instance w/ 6X 6TB HDDs in RAID-Z3. Not the most efficient, but I'm running the drives until they fail.
For backup, I keep several spare drives around and use one of them to back up critical data like my genome, books, music, movies & personal files.
Your post reminds me I need to pull the server and replace a drive that is on its last legs. I use SMART to monitor the health of the drives. This server has been running continuously since 2017. My server is similar to the one described here: