I am building my NAS, which I also intend to use for homelab (currently running everything out of a mini PC). I have setup a Fractal Define R6, with i5-8400, refurbished Intel S4500 240GB SSD for boot, and a refurbished HDD for storing surveillance footage. I think the case can hold up to 8 more HDDs easily, which I can support by adding a PCIE sata expansion card. I will be running everything on Debian, with podman containers and openZFS for ZFS.
My plan is to add 4 x 8TB HDD in RAIDZ2 pool as my primary storage. I am leaning towards RAIDZ2 over mirrored RAID vdevs for more reliability over speed. Both options will give me similar storage capacity I believe. I do want to be able to swap out 8TB drives for 16 TB drives in future or add more drives to increase storage capacity if possible.
For backup, I am not sure if I should add a similar 4 x 8TB RAIDZ2 pool, or if that's overkill. Instead, should I go with a simple 2x16TB mirrored vdev and supplement it with a single 16TB HDD that I plug in once in a while and store offline.
My third stage backup plan is to upload to cloud storage like Backblaze B2 or Amazon S3 glacier deep archive.
Looking for any inputs/advice/recommendation