A Ceph cluster typically consists of several nodes having multiple disk drives. And, these disk drives can be of mixed types. For example, your Ceph nodes might contain disks of the types SATA, NL-SAS, SAS, SSD, or even PCIe, and so on. Ceph provides you with the flexibility to create pools on specific drive types. For example, you can create a high performing SSD pool from a set of SSD disks, or you can create a high capacity, low-cost pool using the SATA disk drives.

In this recipe, we will understand how to create a pool named ssd-pool backed by SSD disks, and another pool named sata-pool, which is backed by SATA disks. To achieve this, we will edit CRUSH maps and make the necessary configurations.

The Ceph cluster that we deployed and have played around with in this book is hosted on virtual machines and does not have real SSD disks backing it. Hence, we will be assuming we have a few virtual disks as SSD disks for learning purposes. There will be no change if you are performing this exercise on a real SSD disk-based Ceph cluster.

For the following demonstration, let's assume that osd.0, osd.3, and osd.6 are SSD disks, and we would be creating an SSD pool on these disks. Similarly, let's assume osd.1, osd.5, and osd.7 are SATA disks, which would be hosting the SATA pool.