Ceph planning tools
Start with a capacity estimate, then check the host layout and the changes needed to reach it. CephClusterGuide's calculator runs in your browser without an account. The accompanying guides explain its assumptions and provide the operational checks that a capacity number alone cannot answer.
Ceph erasure coding calculator
Compare 3x replication with 4+2 and 8+4 erasure coding using your OSD count and drive size. See raw capacity, theoretical usable space and default OSD memory targets. The worked examples explain k+m overhead, host requirements and why metadata and recovery reserves reduce the space available for application data.
Turn the estimate into a cluster plan
Use Ceph hardware requirements to review CPU, memory, disks and networking per host. Compare erasure coding versus replication before choosing a profile: the dropdown compares capacity arithmetic, while the guide explains the workload and recovery tradeoffs.
For an existing cluster, consult pool and placement group configuration to inspect the current replica count and autoscaler settings. Check the pool's eligible hosts and devices before assuming all installed raw capacity is available to it.
Prepare an expansion
The guide to add an OSD to Ceph walks through device inventory, a cephadm preview and rebalance verification. Keep the Ceph warning reference alongside it when checking capacity and PG health before and after the change.