Adding an OSD to CRUSH

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Adding a Ceph OSD to a CRUSH hierarchy is the final step before you might start an OSD (rendering it up and in) and Ceph assigns placement groups to the OSD. You must prepare a Ceph OSD before you add it to the CRUSH hierarchy.

Deployment utilities, such as the Ceph Orchestrator, can prepare a CephOSD before adding it to the CRUSH hierarchy. For example creating a Ceph OSD on a single node:

Syntax

ceph orch daemon add osd HOST:DEVICE,[DEVICE]

The CRUSH hierarchy is notional, so the ceph osd crush add command allows you to add OSDs to the CRUSH hierarchy wherever you wish. The location you specify should reflect its actual location. If you specify at least one bucket, the command places the OSD into the most specific bucket you specify, and it moves that bucket underneath any other buckets you specify.

To add an OSD to a CRUSH hierarchy:

Syntax

ceph osd crush add ID_OR_NAME WEIGHT [BUCKET_TYPE=BUCKET_NAME ...]

Important: If you specify only the root bucket, the command attaches the OSD directly to the root. However, CRUSH rules expect OSDs to be inside of hosts or chassis, and host or chassis should be inside of other buckets reflecting your cluster topology.

If you specify only the root bucket, the command attaches the OSD directly to the root. However, CRUSH rules expect OSDs to be inside of hosts or chassis, and host or chassis should be inside of other buckets reflecting your cluster topology.

The following example adds osd.0 to the hierarchy:

ceph osd crush add osd.0 1.0 root=default datacenter=dc1 room=room1 row=foo rack=bar host=foo-bar-1

Note: You can also use ceph osd crush set or

ceph osd crush
create-or-move

to add an OSD to the CRUSH hierarchy.