406 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
The table columns that are shown in Figure 10-2 on page 405 represent all of the possible 
pool configurations; the rows report in which Easy Tier tier each MDisk tier is mapped. For 
example, consider a pool with all the possible tiers configured that corresponds with the 
T0+T1+T2+T3 configuration in the table in Figure 10-2 on page 405. With this configuration, 
the T1 and T2 are mapped to the same Easy Tier tier. If there is no Tier 0 flash in a storage 
pool, Tier 1 flash is used as the highest performance tier. 
For more information about planning and configuration considerations or best practices, see 
IBM System Storage SAN Volume Controller and Storwize V7000 Best Practices and 
Performance Guidelines, SG24-7521. 
Easy Tier actions
The Easy Tier function continuously monitors volumes for host I/O activity. It collects 
performance statistics for each extent, and derives averages for a rolling 24-hour period of I/O 
activity. Random and sequential I/O rate and bandwidth for reads and writes are collected, as 
well as I/O response time. 
Different types of analytics are used to decide whether extent data migration is required. 
Once per day, Easy Tier analyze the statistics to work out which data should be sent to a 
higher performing tier or might be sent to a tier with lower performance. Four times per day, it 
analyzes the statistics to identify if any data needs to be rebalanced between managed disks 
in the same tier. Once every 5 minutes, Easy Tier checks the statistics to identify if any of the 
managed disks is overloaded. 
All of these analysis phases generate a list of migrations that should be executed. The system 
then spends as long as needed running the migration plan. 
The migration plan can consist of the following actions on volume extents (as shown in 
Figure 10-3):
Figure 10-3   Actions on extents