ZFS manual-ok egyontetuen allitjak, hogy egy fizikai diszk ket kulon zfs pool-ba sose keruljon. A reszletekre nem emlekszem, de nagyon eros javaslat volt. :)
lasd pl. az elso google talalatot: https://superuser.com/questions/1199316/zfs-on-multiple-partitions-on-o…
ZFS is seek-heavy to begin with, because of its copy-on-write design. (This is exacerbated if you use snapshots. Snapshots happen to be a ZFS feature that lots of people really like, even if they don't really use any of ZFS' other features, but they come at a significant cost in terms of risk of data fragmentation, particularly if you make many small writes.)
When you add additional storage to an existing pool, which you would with your proposed scheme, the data already stored is not automatically rebalanced. Instead, ZFS writes new data blocks to vdevs that have the most free space, which causes the data to be distributed across all vdevs over time as it is written. In your case, this means that data will be distributed roughly as you expect: newly written data, including changes to existing files, is more likely to be written to the newly added vdev than to the previously existing vdev(s). Since all vdevs are on the same physical disk, there is no real reliability gain from this; if the single disk dies, then your pool dies, and takes all your data with it.