The setting of a tiering policy for a DP-VOL is optional. If one is not selected, the default is the All(0) tiering policy level. The available levels are listed in Tiering policy levels. DP-VOLs of different tiering policies can coexist in one pool. If you specify the level of the tiering policy, DP-VOLs with the policy are grouped together.

• All(0) is the default policy. In this case, data is stored to all of the tiers.
• When a tier is added to the pool after setting the tiering policy on a DP-VOL, the DP-VOL is relocated according to the new tier lineup.

  For example, if you set the tiering policy to level 5, the data is always allocated to the tier of the low I/O speed. If the pool has two tiers, data is stored in tier 2. If a new tier is added, the number of tiers becomes three and if the new tier is the lowest tier, relocation will be performed to move data into tier 3.

For more information about tiering policy and groups, see Tiering policy levels.