HP XP P9500 Storage - Manual (Page 98)

Reserving tier capacity when setting a tiering policy
If you set the tiering level 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-limit-performance-of-the-tier ÷ the-number-of-pages-in-the-tier
The THP-VOL without a tiering level setting uses the unreserved area in the pool.
98 Configuring thin provisioning