Ceph pools
The concept of pool is not novel in storage systems. Enterprise storage systems are often divided into several pools to facilitate management. A Ceph pool is a logical partition of PGs and by extension Objects. Each pool in Ceph holds a number of PGs, which in turn holds a number of Objects that are mapped to OSDs throughout the cluster. This distribution across cluster nodes helps ensure the required level of RAS. In versions prior to Luminous, the initial Ceph deployment creates by default a pool named rbd
; with Luminous or later you will need to create this yourself if you plan on providing block service. This might not be sufficient for all use-cases and it is recommended to create your own when needed. Deploying RGW or CephFS for your cluster will create the required pools automatically.
A pool guarantees data availability by defining and maintaining a desired number of copies of every object. The type of pool (replicated or erasure coded) determines how many copies of objects...