This is exactly how my desktop PC is setup. I use the HDD ZFS pool to maintain effectively infinite non-expiring snapshots of my (single device) SSD ZFS pool.

This is exactly how my desktop PC is setup. I use the HDD ZFS pool to maintain effectively infinite non-expiring snapshots of my (single device) SSD ZFS pool. If my SSD fails, I can boot directly from the latest backup on the HDD pool.