220 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
However, you can adjust this configuration by setting the number of drives of different classes 
to zero. For information about Easy Tier, see Chapter 10, “Advanced features for storage 
efficiency” on page 403.
If you are adding storage to a pool with storage already assigned, the existing storage is 
taken into consideration. Some properties are inherited from existing arrays for a specific 
drive class. Systems aim to achieve an optimally balanced configuration, so it is not possible 
to add significantly different MDisks to one pool with the given GUI dialog.
For example, if the pool has an array MDisk made of 16 drives of DRAID6, you cannot add 
two drives of RAID1 to the same pool. Otherwise, an imbalanced storage pool is created.
You can still add any array of any configuration to an existing pool by using the CLI. 
When you are satisfied with the configuration presented, click Assign. The RAID arrays, or 
MDisks, are then created and initialized in the background. You can monitor the progress of 
the initialization process by selecting the corresponding task under Running Tasks in the 
upper-right corner of GUI screen, as shown in Figure 6-39. The array is available for I/O 
during this process.
Figure 6-39   Array Initialization task
Click View in the Running tasks list to see the initialization progress and the time that 
remains, as shown in Figure 6-40. Notice that array creation depends on the type of drives it 
consists of. For example, an array of Flash drives is much quicker to initialize than NL-SAS 
drives.
Figure 6-40   Array initialization task progress information