Chapter 10. Advanced features for storage efficiency 409
/SM590000When a volume is migrated out of a storage pool that is managed with Easy Tier, Easy 
Tier automatic data placement mode is no longer active on that volume. Automatic data 
placement is also turned off while a volume is being migrated, even when it is between 
pools that both have Easy Tier automatic data placement enabled. Automatic data 
placement for the volume is reenabled when the migration is complete.
When the system migrates a volume from one storage pool to another, it attempts to 
migrate each extent to an extent in the new storage pool from the same tier as the original 
extent, if possible.
/SM590000When Easy Tier automatic data placement is enabled for a volume, you cannot use the 
svctask migrateexts CLI command on that volume.
10.1.2  Implementing and tuning Easy Tier
The Easy Tier function is enabled by default. It starts monitoring I/O activity immediately after 
storage pool and volumes are created, and starts extent migration as soon as the necessary 
I/O statistics are collected. 
A few parameters can be adjusted. Also, Easy Tier can be switched off on selected volumes 
in storage pools.
MDisk settings
The tier for internal (array) MDisks is detected automatically and depends on the type of 
drives, which are its members. No adjustments are needed.
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.
You can choose the target storage pool and storage tier that is assigned, as shown in 
Figure 10-4.
Figure 10-4   Choosing tier when assigning MDisks
Note: The tier of MDisks mapped from certain types of IBM System Storage Enterprise 
Flash is fixed to tier0_flash, and cannot be changed.