Home > Storage > PowerMax and VMAX > Storage Admin > Dell PowerMax: Data Reduction > System and Storage Resource Pool
Data reduction is set at the system level per storage resource pool (SRP). The data reduction reservation set in the system is used to determine the potential savings from data reduction that can be supported by the available system resources. The data reduction reservation is used by the system to determine how much cache is needed to support the potential effective capacity. The cache used to support effective capacity is allocated as backend metadata in order to support the layout of the storage resource pool. This also determines how the capacity will be used to store data reduced by data reduction. As reduced data fills the compression pools, they expand automatically in order to accommodate more reduced data. Reaching the potential effective capacity relies on data being written to the system is reducible to a level equal to or greater than the data reduction reservation. For example, a system with 100TB of usable capacity where the reservation set is 3.5:1 has a potential effective capacity of 350TB. The written data needs to be reducible to 3.5:1 or better for the system to accommodate 350TB of host data and fit it into 100TB of usable capacity.