HP XP7 Storage - Manual (Page 93)

Reserving tier capacity when setting a tiering policy
If you set the tiering policy of a THP-VOL, the THP-VOL used capacity and the I/O performance
limitation are reserved from the tier. The reserved limit performance per page is calculated as
follows:
The reserved limit performance per page = (The performance limit of the tier) ÷
(The number of pages in the tier)
.
A THP-VOL without a tiering policy setting uses the unreserved area in the pool.
Example of reserving tier capacity
The reservation priority depends on the level of tiering policy. The following figure illustrates the
reservation priority. Tiers are reserved in order of priority from (1) to (7) in the figure. If the pool-VOL
capacity is deficient when you reserve a tier, the nearest tier of your specified tier is allocated. If
you specify two tiers like level 2 or level 4 of the tiering policy, first of all the upper tier is reserved.
At this time, if the capacity of the pool-VOL assigned to the upper tier is deficient, the lower tier
defined by the tiering policy is reserved automatically. For example, in case of level 2 in the
Smart Tiers Z 93