text: For an external MDisk, the tier is assigned when it is added to a storage pool. To assign the 
  MDisk, navigate to**Pools**→**External Storage**, select the MDisk (or MDisks) to add and click 
  **Assign**. 
  
  **Note:**The tier of MDisks mapped from certain types of IBM System Storage Enterprise 
  Flash is fixed to tier0_flash, and cannot be changed. 
  
  You can choose the target storage pool and storage tier that is assigned, as shown in 
  Figure 10-4. 