Chapter 5. CRUSH Map Bucket Types

The second list in the CRUSH map defines bucket types. Buckets facilitate a hierarchy of nodes and leaves. Node (or non-leaf) buckets typically represent physical locations in a hierarchy. Nodes aggregate other nodes or leaves. Leaf buckets represent ceph-osd daemons and their corresponding storage media.

Adding, modifying or removing a bucket type involves editing a CRUSH Map. To add a bucket type to the CRUSH map, create a new line under your list of bucket types. Enter type followed by a unique numeric ID and a bucket name. By convention, there is one leaf bucket and it is type 0; however, you may give it any name you like (e.g., osd, disk, drive, storage, etc.).

#types
type {num} {bucket-name}

For example:

# types
type 0 osd
type 1 host
type 2 chassis
type 3 rack
type 4 row
type 5 pdu
type 6 pod
type 7 room
type 8 datacenter
type 9 region
type 10 root