The number of clusters in your system varies, depending on several factors, such as:
The logical divisions for the databases in your system, where clusters that are created, and zones that are members of those clusters, might have different functions or audiences.
The number of zones that are available and the number of clusters that can be created with those zones as members, which is partly determined by several factors, such as the number of Database Domains on each PDomain, the size of each Database Domain, and so on.
See Guidelines for Planning Zones for more information on how to decide on the total number of zones and clusters in your system.
Once you determine the number of clusters in your system, you can now determine the maximum amount of space that you can assign to each cluster based on the total amount of usable storage that is available. The total amount of space that you assign to all the clusters in the system cannot exceed the total amount of storage that is available.
For example, assume you have a total amount of 48 TB available as usable storage, and you want to create four clusters total in your system, where each cluster has the same overall size. Then the maximum amount of usable space for each cluster would be 12 TB apiece.