[ceph-users] Placement of block/db and WAL on SSD?

Nautilus install. Documentation seems a bit ambiguous to me - this is for a spinner + SSD, using ceph-volume If I put the block.db on the SSD with     "ceph-volume lvm create --bluestore --data /dev/sdd --block.db /dev/sdc1" does the wal exists on the ssd (/dev/sdc1) as well, or does it remain on the hdd (/dev/sdd)? Conversely, what happens with the block.db if I place the wal with --block.wal Or do I have to setup separate partitions for the block.db and wal? -- Lindsay