Tiering policy
The tiering policy function is used to assign a specific storage tier to a specific DP-VOL. A tiering policy specifies subset of tiers that is available to a given set of DP-VOLs.
Tier relocation changes the location of previously stored data. It is performed in conformance to the tiering policy. If a DP-VOL is initially allocated to a low-speed tier and the tiering policy is changed to a high-speed tier, relocation is performed in the next cycle.
For example, if you set the tiering policy level on a V-VOL (DP-VOL) to a tier with a high I/O speed, the data is always stored on the high-speed tier when relocating tiers. When you use that V-VOL (DP-VOL), regardless of the actual size of the I/O load, you can always get high-speed responses. See Tiering policy levels.
When you create the DP-VOL, you can designate one of six existing tiering policies and define up to 26 new tiering policies. See Tiering policy levels and Setting tiering policy on a DP-VOL.
Use the Edit LDEVs window to change the tiering policy settings. When tier relocation occurs, the related tiering policy set for the DP-VOL is used to relocate data to the desired tier or tiers.
The tiering policy does not own pool capacity. Rather, pool capacity is shared among tiers. Pages are allocated in order of priority from upper to lower tiers in a tiering policy. When you specify a new allocation tier, pages are allocated starting from the tier that you specify.
The tier range, frequency distribution, and used capacity are displayed per tiering policy: existing tier level All(0), Level1(1) through Level5(5), and Level6(6) to Level31(31).