I’m in the same boat, I use Jellyfin where I can but Plex is still so much better for sharing, especially with non-technical people so I run both. Really hoping the Jellyfin folks realize they can sell a relay service to make some money and fund their development to improve the app. Seems to be working well for Homeassistant!

Oh, forgot to mention: striping in ZFS will use the capacity of the smallest drive. It sounds like you have a 1TB drive and a 4TB drive, so striping would give you access to 2TB at most.

Losing one drive in a striped pool with no redundancy means the entire pool is shot. Restoration from your HDDs may take a very long time, on top of data loss between the time of failure and your last snapshot. Striping without redundancy is fast, but dangerous.

This may work at first, and maybe you really do have a use case where this kind of failure is tolerable. However, in my experience, data is precious more often than it isn’t. Over time, you’re more likely to find use cases where the loss of the pool will be frustrating at best, and devastating at worst.

If you’re not using any redundancy, I would create separate pools so each drive can fail independently. You’ll have all 5TB of storage, but not contiguously. That at least constrains the failure modes you’re likely to run into.

If you are striping with redundancy (e.g., RAID-Z1), which I would highly recommend, you can lose a drive and not lose any data. That would take at least 3 equally-sized drives though, and you’d only be able to use the capacity of 2 of them.