Chapter 10. Advanced features for storage efficiency 413
This can be done only by using the CLI. Use the lsvdisk command to check and the chvdisk 
command to modify Easy Tier function status on a volume copy, as shown in Example 10-4.
Example 10-4   Checking and modifying Easy Tier settings on a volume
IBM_Storwize:ITSO-V7k:superuser>lsvdisk  vdisk0 |grep easy_tier
easy_tier on
easy_tier_status balanced
IBM_Storwize:ITSO-V7k:superuser>chvdisk -easytier off vdisk0
IBM_Storwize:ITSOV7K:superuser>
System-wide settings
There is a system-wide setting Easy Tier acceleration that is disabled by default. Turning it on 
makes Easy Tier move extents up to four times faster than the default setting. In accelerate 
mode, Easy Tier can move up to 48 GiB per 5 minutes, whereas in normal mode it moves up 
to 12 GiB. The following use cases are the most probable use cases for acceleration:
/SM590000When adding capacity to the pool, accelerating Easy Tier can quickly spread volumes onto 
the new MDisks.
/SM590000Migrating the volumes between the storage pools when the target storage pool has more 
tiers than the source storage pool, so Easy Tier can quickly promote or demote extents in 
the target pool.
This setting can be changed online, but only by using the CLI. To turn on or off Easy Tier 
acceleration mode, use the chsystem command. Use the lssystem command to check its 
current state, as shown in Example 10-5.
Example 10-5   The chsystem command
IBM_Storwize:ITSOV7K:superuser>lssystem |grep easy_tier
easy_tier_acceleration off
IBM_Storwize:ITSOV7K:superuser>chsystem -easytieracceleration on
IBM_Storwize:ITSOV7K:superuser>
10.1.3  Monitoring Easy Tier activity
When Easy Tier is active, it constantly monitors and records I/O activity, collecting extent heat 
data. Heat data files are produced approximately once a day and summarize the activity per 
volume since the last heat data file was produced. 
The IBM Storage Tier Advisor Tool (STAT) is a Windows console application that can analyze 
heat data files that are produced by Easy Tier and produce a graphical display of the amount 
of “hot” data per volume and predictions of how more Solid-State Drive (T0) capacity, 
Enterprise Drive (T1), and Nearline Drive (T2) might benefit performance for the system and 
by storage pool. 
Note: Thin-provisioned and compressed volumes in a data reduction pool cannot have 
Easy Tier switched off. It is possible to switch off Easy Tier only at a pool level.
Note: Enabling Easy Tier acceleration is advised only during periods of low system activity 
only after migrations or storage reconfiguration occurred. It is recommended to keep Easy 
Tier acceleration mode off during normal system operation.