When you are operating a Ceph cluster, it's important to monitor its health and performance. By monitoring Ceph, you can be sure that your cluster is running at full health and also be able to quickly react to any issues that may arise. By capturing and graphing performance counters, you will also have the data that's required to tune Ceph and observe the impact of your tuning on your cluster.

In this chapter, you will learn about the following topics:

• Why it is important to monitor Ceph
• How to monitor Ceph's health by using the new built-in dashboard
• What should be monitored
• The states of PGs and what they mean
• How to capture Ceph's performance counters with collectd
• Example graphs using Graphite