HP XP P9500 Storage - Manual (Page 76)

performance utilization percent shows 100%, this indicates that the target I/O load to a
tier is beyond the limit performance value.
CAUTION: The limit performance value is proportional to the capacity of the pool volume
used in the tier. The total capacity of the parity groups should be used for a pool to further
improve the limit performance.
2. Determine the tier delta values
The tier range values are set as the lower limit boundary of each tier. The delta values
are set above and below the tier boundaries (+10 to 20%) to prevent pages from being
migrated unnecessarily. If all pages subject to tier relocation can be contained in the
upper tier, both the tier range value (lower limit) and the delta value will be zero.
The following figure illustrates the relationship between the tier range and the delta value.
3. Determine the target tier of a page
The IOPH recorded for the page is compared against the tier range value to determine
the tier to which the page moves.
5. Migrate the pages
The pages move to the appropriate tier. After migration, they are rebalanced. I/Os that occur
due to page migration are not monitored.
Tier relocation rules, restrictions, and guidelines
Rules
•
Performance monitoring, using both Auto and Manual execution modes, observes only the
pages that were allocated to THP V-VOLs prior to the start of the monitoring cycle. Those pages
not in use prior to the start of monitoring are not candidates for tier relocation, even if they
are subsequently allocated during the monitoring cycle.
•
Tier relocation can be performed concurrently on up to eight pools pools. If more than eight
pools are specified, relocation of the ninth tier starts after relocation of any of the first eight
pools have completed.
•
If Auto execution mode is specified, performance monitoring may stop about one minute
before to one minute after the beginning of the next monitor cycle start time.
•
The amount of relocation varies per cycle. In some cases, the cycle may end before relocation
could be handled. In these cases, a subsequent cycle will relocate the appropriate pages.
•
Calculating the tier range volumes will be influenced by capacity allocated to THP V-VOLs
with relocation disabled and the buffer reserve percentages.
76 Configuring thin provisioning