422 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
As with RACE, the new implementation uses the same Lempel-Ziv (LZ) based real-time 
compression and decompression algorithm. However, in contrast to RACE compression, 
DRP compression operates on smaller block sizes, which results in more performance gains.
The third benefit of DRP comes in the form of performance improvements because of Easy 
Tier. 
The metadata of data reduction pools does not fit in RAM; therefore, it is stored on disk on 
metadata volumes, which are separate from data volumes. The metadata volumes of data 
reduction pools are small and frequently accessed. They are good candidates for promotion 
through Easy Tier. In contrast, data volumes are large, but because the metadata is stored 
separately, Easy Tier can accurately identify frequently used data. Performance gains are 
expected because Easy Tier promotes metadata to the fastest available storage tier.
DRPs support end-to-end SCSI Unmap functionality. Space that is freed from the hosts is a 
process called unmap. A host can issue a small file unmap (or a large chunk of unmap space 
if you are deleting a volume that is part of a data store on a host) and these result in the 
freeing of all the capacity allocated within that unmap. Similarly, deleting a volume at the DRP 
level frees all of the capacity back to the pool. 
When a data reduction pool is created, the system monitors the pool for reclaimable capacity 
from host unmap operations. This capacity can be reclaimed by the system and redistributed 
into the pool. Create volumes that use thin provisioning or compression within the data 
reduction pool to maximize space within the pool. 
10.4.3  Implementing DRP with compression and deduplication
The implementation process for DRPs is similar to standard pools, but has its own specifics.
Creating pools and volumes
To create a DRP, select Data Reduction Enable in the Create Pool dialog, which is available 
be clicking Pools → Pools. For more information about how to create a storage pool and 
populate it with MDisks, see Chapter 6, “Storage pools” on page 191.
There is a maximum number of four DRPs in a system. When this limit is reached, no other 
DRPs can be created.
A DRP uses metadata. Even when there are no volumes in the pool, some of the space of the 
pool is used to store the metadata. Regardless of the type of volumes the pool contains, 
metadata is always stored separate from customer data.
Metadata capacity depends on the total capacity of a storage pool and on a pool extent size. 
This should be considered when planning capacity.
The main purpose of DRPs is to be a fast and efficient container for volumes with data 
reduction capability. DRPs can also contain standard thick provisioned volumes.
To create a volume on a DRP, navigate to Volumes → Volumes, and click Create Volumes.
Note: If your DRP has a total capacity of less than 50 TB savings, you might need to 
decrease the extent size from the default for DRP (which is 4 GB) to 1 GB for optimal 
space.