To create a BlueStore OSD using ceph-volume, you run the following command, specifying the devices for the data and RocksDB storage. As previously mentioned, you can separate the DB and WAL parts of RocksDB if you so wish:

ceph-volume create --bluestore /dev/sda --block.wal /dev/sdb --block.db /dev/sdc (--dmcrypt)

The preceding code assumes that your data disk is /dev/sda. For this example, assume that you are using a spinning disk, and that you have a faster device, such as an SSD (/dev/sdb) and a very fast NVMe device (/dev/sdc). The ceph-volume tool 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 then place a link to the SSD to store the RocksDB on it and a link to the NVMe device to store the WAL. You can create multiple OSDs sharing the same SSD for DB and WAL by partitioning the devices, or by using lvm to carve logical volumes out of them.

However, as we discovered in Chapter 2, Deploying Ceph with Containers, using a proper deployment tool for your Ceph cluster helps to reduce deployment time and ensures consistent configuration across the cluster. Although the Ceph Ansible modules also support deploying BlueStore OSDs, at the time of writing, it doesn't currently support automatically creating multiple DB and WAL partitions on a single device.

Now that you understand how to create BlueStore OSD's the next topic that is required to be discussed is the upgrading of an existing cluster.