Considerations before adding or removing a node

Ceph OSD nodes can be added or removed at run time. This means that you can resize the storage cluster capacity or replace hardware without taking down the storage cluster. Understand these considerations before adding or removing a node.

The ability to serve Ceph clients while the storage cluster is in a degraded state also has operational benefits. For example, you can add or remove or replace hardware during regular business hours, rather than working overtime or on weekends. However, adding and removing Ceph OSD nodes can have a significant impact on performance.

Before you add or remove Ceph OSD nodes, consider the effects on storage cluster performance:

• Whether you are expanding or reducing the storage cluster capacity, adding or removing Ceph OSD nodes induces backfilling as the storage cluster rebalances. During that rebalancing time period, Ceph uses additional resources, which can impact storage cluster performance.

• In a production Ceph storage cluster, a Ceph OSD node has a particular hardware configuration that facilitates a particular type of storage strategy.

• Since a Ceph OSD node is part of a CRUSH hierarchy, the performance impact of adding or removing a node typically affects the performance of pools that use the CRUSH ruleset.