A drive extent within a dynamic pool is simply a portion of a drive that is gigabytes in size. The size of each extent is fixed for each drive type. After a dynamic pool is created on the system, each drive within a dynamic pool is partitioned into drive extents. The number of extents created on each drive directly depends on the drive type and size. Each extent within a drive is either used to store user data, or reserved as space to replace a failing or faulted drive within the pool.
Figure 4 shows two drives, a 400 GB SAS FLASH 3 drive and an 800 GB SAS flash 3 drive, partitioned into drive extents. Since all drive extents for this drive type are equal in size, the number of extents created on the 800 GB drive is twice the number created on the 400 GB drive.