HP XP7 Storage - Manual (Page 95)

Notes on tiering policy settings
•
If Auto is set as the execution mode, tier relocation is performed based on the monitoring
cycle. Therefore, when the tiering policy setting is changed, tier relocation will automatically
implement the tiering policy at the end of the current monitoring cycle. See Example 1 in
“Execution mode settings and tiering policy” (page 100) .
•
If Manual is set as the execution mode, you must manually perform monitoring, issue a monitor
stop, and then start relocation (see Example 2, Case 1, in
“Execution mode settings and tiering
policy” (page 100) ). 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” (page 100) ). Therefore, you do not need to perform new
monitoring.
•
If a capacity shortage exists in the tier being set, a message may appear in the View Tier
Property window that the page allocation cannot be completed according to the tiering policy
specified for the V-VOL. Should that occur, the page allocation in the entire pool -- including
the tier that defines the tiering policy -- might not be optimized.
NOTE: The 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) which is 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 may not be allocated in
conformance to the tiering policy specified for the V-VOL. In that case, 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.
Allocation capacity considerations Tiering Policy
Tier range and I/O performance All(0), Level2(2), or Level4(4)
Tier range Level1(1), Level3(3), or Level5(5)
First phase: Tier range. From Level6(6) to Level31(31)
Smart Tiers Z 95