Figure 6-4 Create Pool dialog box Figure 6-5 Advanced pool settings Mark the  Data Reduction  check box to create the Data Reduction Pool. Leaving it unmarked  creates a standard storage pool. A standard storage pool that is created by using the GUI has a default extent size of 1 GB.  Data Reduction Pools have a default extent size of 4 GB. The size of the extent is selected at  creation time and cannot be changed later.  If you want to specify a different extent size, you can enable this option by clicking  Settings GUI Preferences General  and checking  Advanced pool settings , as shown in  Figure 6-5. When advanced pool settings are enabled, you can additionally select an extent size at  creation time, as shown in Figure 6-6 on page 195. 194  Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1