Figure 3-18 shows the DRP Compression I/O Amplification. Figure 3-18 I/O Amplification of space allocated (assumes 50% compression rate) Note:  Writes to already allocated space will drive the need for Garbage Collection (GC).  The cost of GC depends on the amount of valid data in the extent that has not been  overwritten. 3.3 RACE compared to Data Reduction Pools RACE uses a variable input with a fixed output of the inbound data stream, all of which is  inline without any post process. However, RACE has to wait intermittently or pause to see if  more I/O is coming for a particular volume, as shown in Figure 3-19 on page 41. The RACE  minimum block size to read from the back end is 32 KB. One of the benefits of RACE is that it enables at least 4 - 8 times more data through  decompression hardware than DRP, for a true random workload. However, DRP Compression  uses fixed input with a variable output, or the opposite of RACE.  As shown in Figure 3-20 on page 41, the DRP maximum block size to read from the back end  is 8 KB (typically 4 KB or less though). With the use of 8 KB input sizes, there is a small loss  in compression ratio but a gain in lower latency when all workloads are put into the same  predictable small block size.  Host I/O that is put in these small-grained block sizes in DRP results in the following  functionality:  GLYPH<SM590000> Enables fine-grained allocation of block data GLYPH<SM590000> Provides the ability to free back unused capacity at a fine grain GLYPH<SM590000> Gives consistent, predictable performance GLYPH<SM590000> Optimizes performance for Flash storage  40  IBM FlashSystem 9100 Architecture, Performance, and Implementation