To create a BlueStore OSD, you can use ceph-disk that fully supports creating BlueStore OSDs with either the RocksDB data and WAL collocated or stored on separate disks. The operation is similar to when creating a filestore OSD except instead of specifying a device for use as the filestore journal, you specify devices for the RocksDB data. As previously mentioned, you can separate the DB and WAL parts of RocksDB if you so wish:
ceph-disk prepare --bluestore /dev/sda --block.wal /dev/sdb --block.db /dev/sdb
The preceding code assumes that your data disk is /dev/sda. For this example, assume a spinning disk and you have a faster device such as SSD as /dev/sdb. Ceph-disk would create two partitions on the data disk: one for storing the actual Ceph objects and another small XFS partition for storing details about the OSD. It would also create two partitions for SSD for the DB and WAL. You can create...