Mastering Ceph - Second Edition

Replicated pools

Replicated RADOS pools are the default pool type in Ceph; data is received by the primary OSD from the client and then replicated to the remaining OSDs. The logic behind the replication is fairly simple and requires minimal processing to calculate and replicate the data between OSDs. However, as the data is replicated in whole, there is a large write penalty, as the data has to be written multiple times across the OSDs. By default, Ceph will use a replication factor of 3x, so all data will be written three times; this does not take into account any other write amplification that may be present further down in the Ceph stack. This write penalty has two main drawbacks: It obviously puts further I/O load on your Ceph cluster, ...