The following are a few best practices to keep a Ceph cluster running healthy:

• If possible, keep all settings to default for a healthy cluster.
• Use Ceph pool only to implement a different OSD type policy and not for multitenancy, such as one pool for SSDs and another for HDDs.
• Do not make frequent Ceph configuration changes. It adds extra workload on the cluster OSDs, reducing the life of HDDs. After each change, let the cluster rebalance data before making new changes. 
• Always keep in mind the core count of Ceph nodes when adjusting Ceph threads. Do not let the number of threads become more than the core count.
• In a small Ceph cluster, SSDs will increase write performance. In a large cluster, a higher OSD count will increase performance.
• Do not use desktop class hard drives as OSDs in a small cluster.
• Reduce backfill and recovery threads to a minimum to continue recovery without hurting client request performance.