With storage efficiency, DRP thin and compressed volumes provide the best performance  numbers. This is due to the new compression implementation, because this provides better  load balancing and consistent performance.  Figure 3-15 shows the types of volumes in the DRP pools. There are four main characteristics that make up the IBM Data Reduction Pool design: A data reduction pool, at its core, uses an LSA to allocate capacity. Therefore, the volume that  you create from the pool to present to a host application consists of a directory that stores the  allocation of blocks within the capacity of the pool.  All writes for data reduction pools take place at the upper cache layer to the host. Reads have  to go through the lower cache layer. The heart of the new DRP functionality is in the new  implementation of the Log Structured Array. This includes lower cache, virtualization, Easy  Tier, and RAID. LSA understands what works best for each of these components. A log structured array allows a “tree-like” directory to be used to define the physical  placement of data blocks independent of size and logical location. Each logical block device  has a range of logical block addresses (LBAs). Starting from 0 and ending with the block  address that fills the capacity. When written, an LSA allows you to allocate data sequentially  and provide a directory that provides a lookup to match the logical block address with the  physical address within the array.  Note:  LSA always appends new data to the end of the array. When data is overwritten, the  old location and capacity utilized needs to be marked as  free . UNMAP functions can also  request that you  free  no longer needed capacity. Compression overwrites can result in a  different capacity being used. Deduplication might find new duplicates when data is  rewritten. GLYPH<SM590000> Fine-grained allocation of data blocks GLYPH<SM590000> The ability to free back unused (unmapped or overwritten) capacity at a fine grain GLYPH<SM590000> Give consistent, predictable performance GLYPH<SM590000> Optimize performance for solid state storage, such as Flash Figure 3-15 Volume types Chapter 3. Data reduction and tools  37