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.