Chapter 9. Advanced features for storage efficiency 443
9.2.3 Easy Tier process
Easy Tier is based on an algorithm with a threshold to evaluate if an extent is cold, warm, or
hot. Easy Tier consists of four main processes. These processes ensure that the extent
allocation in multi-tiered storage pools is optimized for the best performance, based on your
workload in the last 24 hours. The processes are listed:
I/O Monitoring
Data Placement Advisor
Data Migration Planner
Data Migrator
Figure 9-4 shows the flow between these processes.
Figure 9-4 Easy Tier process flow
The four main processes and the flow between them are described in the following sections.
9.2.4 I/O Monitoring
The I/O Monitoring (IOM) process operates continuously and monitors host volumes for I/O
activity. It collects performance statistics for each extent at 5-minute intervals and derives
averages for a rolling 24-hour period of I/O activity.
Easy Tier permits large block I/Os and considers only I/Os up to 64 KB as migration
candidates.
IOM is an efficient process and adds negligible processing impact to the IBM Storwize V5000
Gen2 node canisters.
9.2.5 Data Placement Advisor
The Data Placement Advisor (DPA) uses workload statistics to make a cost benefit decision
about the extents that need to be candidates for migration to a higher-performance tier.
This process also identifies extents that must be migrated back to a lower tier.
9.2.6 Data Migration Planner
By using the previously identified extents, the Data Migration Planner (DMP) process builds
the extent migration plan for the storage pool.
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