Adding a bucket

Add a bucket type for each CRUSH hierarchy.

To add a bucket instance to your CRUSH hierarchy, specify the bucket name and its type. Bucket names must be unique in the CRUSH map.

ceph osd crush add-bucket {name} {type}

If you plan to use multiple hierarchies, for example, for different hardware performance profiles, consider naming buckets based on their type of hardware or use case.

For example, you could create a hierarchy for solid state drives (ssd), a hierarchy for SAS disks with SSD journals (hdd-journal), and another hierarchy for SATA drives (hdd):

ceph osd crush add-bucket ssd-root root
ceph osd crush add-bucket hdd-journal-root root
ceph osd crush add-bucket hdd-root root

The Ceph CLI outputs:

added bucket ssd-root type root to crush map
added bucket hdd-journal-root type root to crush map
added bucket hdd-root type root to crush map

Add an instance of each bucket type you need for your hierarchy. The following example demonstrates adding buckets for a row with a rack of SSD hosts and a rack of hosts for object storage.

ceph osd crush add-bucket ssd-row1 row
ceph osd crush add-bucket ssd-row1-rack1 rack
ceph osd crush add-bucket ssd-row1-rack1-host1 host
ceph osd crush add-bucket ssd-row1-rack1-host2 host
ceph osd crush add-bucket hdd-row1 row
ceph osd crush add-bucket hdd-row1-rack2 rack
ceph osd crush add-bucket hdd-row1-rack1-host1 host
ceph osd crush add-bucket hdd-row1-rack1-host2 host
ceph osd crush add-bucket hdd-row1-rack1-host3 host
ceph osd crush add-bucket hdd-row1-rack1-host4 host

Once you have completed these steps, view your tree.

ceph osd tree

Notice that the hierarchy remains flat. You must move your buckets into a hierarchical position after you add them to the CRUSH map.