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Data Reduction: The use of compression, deduplication and pattern detection to reduce capacity usage and the cost of physical storage. In systems prior to the release of Dell EMC PowerMax, data reduction is compression only.
Data Reduction Reservation: A system Cache reservation used to determine the maximum savings that can be achieved when data reduction is enabled. This reservation acts as a system guardrail for management of resources such as disk capacity and cache in order to maintain a balance between performance and efficient capacity usage.
Storage Group Compression Ratio: The compression ratio displayed for allocations related to a specific storage group. This value may be greater than or less than the system or storage resource pool data reduction ratio displayed in management application displays.
Compressibility: The maximum compression ratio that may be achieved for either a storage group or a device. This value may be presented as a higher value than current savings due to the design activity-based compression (see Activity Based Compression).
Data Reduction Ready: The state of the system when the default storage resource pool (SRP) can store compressed data. For a system to be able to compress data it must have one compression I/O module per director, have compression enabled and have a system data reduction reservation ratio set.
Data Reduction Capable: A system installed with at least the Q1 2018 PowerMaxOS where the data reduction reservation applied to the system IMPL is 1.0:1.
Compression Pool: The collection of data devices configured within the physical disks where the track size is the same. For example, the 64KB pool is made up of data devices where all the device’s tracks are 64KB in size.
Terabytes Usable (TBu): The backend usable storage capacity in the absence of compression referring to the amount of physical storage in the system.
Example: 50 TBu is 50 Terabytes of usable physical storage.
Terabytes Effective (TBe): The front-end effective storage capacity in the presence of data reduction. This represents the potential maximum amount of host or application data that can be written to the array.
Example: 50 TBu of physical storage with a data reduction reservation of 3:1 translates to 150 TBe. The total TBe value can be achieved assuming the data consuming capacity on the array is reducible at a level equal to or greater than the data reduction reservation set in the system.