The management of data as it flows through a Ceph cluster involves each of the components we have discussed so far. Coordination among these components empowers Ceph to provide a reliable and robust storage system. Data management begins with clients writing data to pools. When a client writes data to a Ceph pool, the data is sent to the primary OSD. The primary OSD commits the data locally and sends an immediate acknowledgement to the client if replication factor is 1. If the replication factor is greater than 1 (as it should be in any serious deployment) the primary OSD issues write subops to each subsidiary (secondary, tertiary, etc) OSD and awaits a response. Since we always have exactly one primary OSD, the number of subsidiary ...
Ceph data flow
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