We already covered Ceph CRUSH maps in Chapter 4, Ceph Internals. In this section, we will dive into the details of CRUSH maps, including their layouts, as well as defining custom CRUSH maps. When you deploy a Ceph cluster using the procedure mentioned in this book, it will create a default CRUSH map for your Ceph cluster. This default CRUSH map is good to go for sandbox and testing environments. However, if you run Ceph clusters in production or at a large scale, consider developing a custom CRUSH map for your environment to ensure better performance, reliability, and data security.