HP XP P9500 Storage - Manual (Page 74)

Explanation of the relocation flow:
1.
Allocate pages and map them to THP V-VOLs
Pages are allocated and mapped to THP V-VOLs on an on-demand basis. Page allocation
occurs when a write is performed to an area of any THP V-VOL that does not already have a
page mapped to that location. A free page is selected for allocation from an upper tier with
a free page. If the capacity of all the tiers is insufficient, an error is sent to the host.
2. Gather I/O load information of each page
Performance monitoring gathers monitoring information of each page in a pool to determine
the physical I/O load per page in a pool. I/Os associated with page relocation, however,
are not counted.
3. Create frequency distribution graph
The frequency distribution graph, which shows the relationship between I/O counts (I/O load)
and capacity (total number of pages), is created. You can use the Tier Properties window in
Remote Web Console to view this graph. The vertical scale of the graph indicates ranges of
I/Os per hour and the horizontal scale indicates a capacity that received the I/O level. Note
that the horizontal scale is accumulative.
CAUTION: When the number of I/Os is counted, the number of I/Os satisfied by cache hits
are not counted. Therefore, the number of I/Os counted by Performance Monitoring is different
from the number of I/Os from the host. The number of I/Os per hour is shown in the graph.
If the monitoring time is less than an hour, the number of I/Os shown in the graph might be
higher than the actual number of I/Os.
The following is an example of a frequency distribution graph.
74 Configuring thin provisioning