Notes on tiering policy settings

• If Auto is set as the execution mode, tier relocation is performed based on the monitoring cycle. When the tiering policy setting changes, tier relocation implements the tiering policy at the end of the current monitoring cycle. See Example 1 in Execution mode settings and tiering policy.

• If Manual is set as the execution mode, you must manually perform monitoring, issue a monitor stop, then start relocation (see Example 2, Case 1, in Execution mode settings and tiering policy). If you change the tiering policy settings while obtaining monitoring data, the monitoring data is used for the next tier relocation (see Example 2, Case 2, in Execution mode settings and tiering policy). Therefore, you do not need to perform new monitoring.

• If a capacity shortage exists in the tier being set, a message can appear in the View Tier Property window that the page allocation cannot be completed according to the tiering policy specified for the V-VOL. The page allocation in the entire pool, including the tier that defines the tiering policy, may not be optimized.

 a message that page allocation cannot be completed according to the tiering policy does not appear when these tiering policies are set:

• All(0)

• In a 2-tier configuration, Level2(2), Level3(3), or Level4(4), equivalent to All(0)

When a capacity shortage exists in a tier, you can revise the setting of the tiering policy or the configuration of tiers. If the capacity of one tier is fully exhausted, the migrating pages are assigned to the next tier according to the tiering policy.

• Level1(1): When tier 1 is full, the remaining pages are allocated to tier 2. If tier 2 is full, the remaining pages are allocated to tier 3.

• Level3(3): When tier 2 is full, the remaining pages are allocated to tier 1. If tier 1 is full, the remaining pages are allocated to tier 3.

• Level5(5): When tier 3 is full, the remaining pages are allocated to tier 2. If tier 2 is full, the remaining pages are allocated to tier 1.

• Level2(2), Level4(4), and from Level6(6) to Level31(31): When the specified tier is full, the unallocated pages are kept in the prior tier or they are allocated to the tier that has free space.

• If a performance shortage exists in the tier being set, pages can not be allocated in conformance with the tiering policy specified for the V-VOL. Pages are allocated according to the performance ratio of each tier.

As shown in the following table, allocation capacity considerations are based on the tiering policy.