Embodiments relate to cluster-centric tiered storage with a flexible tier definition to support performance of transactions. Object data is distributed in a multi-tiered shared-nothing cluster. Hierarchical tiers of data storage are assigned different roles within the hierarchy. The tiers are arranged according to a number of cycles required to access a tier. The tiers are managed globally across the cluster and objects are placed in tiers according to a flexible tier definition and the tier arrangement. The probability of object access is computed for objects, and objects are placed on different tiers responsive to the computation and the number of cycles required to access the tier. Objects are moved between tiers responsive to a probability frequency of object access.