HP XP P9500 Storage - Manual (Page 72)

If the performance utilization percent shows 100%, this indicates that the target I/O load
to a tier is beyond the forecasted limit performance value.
CAUTION: The limit performance value is proportional to the capacity of the pool
volumes used in the tier. The total capacity of the parity group 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.
3. Determine the target tier of a page for relocation.
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, the page usage rates are averaged
out in all tiers. I/Os which occur in the page migration are not monitored.
Tier relocation rules, restrictions, and guidelines
Rules
•
Performance monitoring, using both Auto and Manual execution modes, observes the pages
that were allocated to THP V-VOLs prior to the start of the monitoring cycle and the new pages
allocated during the monitoring cycle. Pages that are not allocated during performance
monitoring are not candidates for tier relocation.
•
Tier relocation can be performed concurrently on up to eight pools. If more than eight pools
are specified, relocation of the ninth pool starts after relocation of any of the first eight pools
has 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 all
relocation can be handled. If tier relocation doesn't finish completely within the cycle, relocation
to appropriate pages is executed in the next cycle.
•
Calculating the tier range values will be influenced by the capacity allocated to THP V-VOLs
with relocation disabled and the buffer reserve percentages.
•
While a pool-VOL is being deleted, tier relocation is not performed. After the pool-VOL deletion
is completed, tier relocation starts.
72 Configuring thin provisioning