Examining the Ceph configuration setting that controls the maximum number of Placement Groups (PGs) allowed per Object Storage Daemon (OSD) is a crucial administrative task. This setting dictates the upper limit of PGs any single OSD can manage, influencing data distribution and overall cluster performance. For instance, a cluster with 10 OSDs and a limit of 100 PGs per OSD could theoretically support up to 1000 PGs. This configuration parameter is typically adjusted via the `ceph config set mon mon_max_pg_per_osd` command.
Proper management of this setting is vital for Ceph cluster health and stability. Setting the limit too low can lead to uneven PG distribution, creating performance bottlenecks and potentially overloading some OSDs while underutilizing others. Conversely, setting the limit too high can strain OSD resources, impacting performance and potentially leading to instability. Historically, determining the optimal value has required careful consideration of cluster size, hardware capabilities, and workload characteristics. Modern Ceph deployments often benefit from automated tooling and best-practice guidelines to assist in determining this crucial setting.
