Chapter 10. Advanced features for storage efficiency 407
/SM590000Promote
Moves the hotter extents to the MDisks (ranks) of the higher-performance tier with 
available capacity. Promote occurs within adjacent tiers. 
/SM590000Demote
Demotes colder extents from the higher tier to the lower tier. Demote occurs within 
adjacent tiers.
/SM590000RB-Move (Auto Rebalance)
Auto-rebalance, which is also known as intra-tier rebalancing, is a capability of Easy Tier 
that automatically rebalances the workload across all MDisks of a storage tier within a 
managed extent pool. It also automatically populates new ranks that were added to the 
pool. 
/SM590000Warm demote
Easy Tier continuously ensures that the higher performance tier does not suffer from 
saturation or overload conditions that might affect the overall performance in the pool. This 
action is triggered when bandwidth or IOPS exceeds a predefined threshold of an MDisk 
and causes the movement of selected extents from the higher-performance tier to the 
lower-performance tier to prevent MDisk overload.
/SM590000Cold demote
Easy Tier automatically locates and demotes inactive (or cold) extents that are on a higher 
performance tier to its adjacent lower-cost tier. In that way, it automatically frees extents on 
the higher storage tier before the extents on the lower tier become hot, and then helps the 
system to be more responsive to new hot data.
Cold demote occurs between tiers 2 and 3 only.
/SM590000Expanded cold demote
Demotes appropriate sequential workloads to the lowest tier to better use nearline tier 
bandwidth.
/SM590000Swap
A swap moves a “hot” extent from a lower performance disk tier to a higher disk tier while 
simultaneously moving a “cold” extent from the higher disk tier to a lower performance disk 
tier.
Extent migration occurs at a maximum rate of 12 GB every 5 minutes for the entire system. It 
prioritizes the following actions:
/SM590000Promote and rebalance get equal priority
/SM590000Demote is guaranteed 1 GB every 5 minutes, and then gets whatever is left
The Easy Tier overload protection is designed to avoid overloading any type of MDisk with too 
much work. To achieve this, Easy Tier needs to have an indication of the maximum capability 
of a managed disk. 
For an array made of locally attached drives, the system can calculate the performance of the 
MDisk because it is pre-programmed with performance characteristics for different drives. For 
a SAN-attached managed disk, the system cannot calculate the performance capabilities, so 
the system has a number of predefined levels that can be configured manually for each 
MDisk. This is called the Easy Tier load parameter (low, medium, high, very_high). 
Note: Extent promotion or demotion only occurs between adjacent tiers. In a three-tier 
storage pool, Easy Tier does not move extents from a flash tier directly to nearline tier or 
vice versa without moving to the enterprise tier first.