HP XP P9500 Storage - Manual (Page 83)

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. Normally, a free page is selected for allocation from an upper
tier with a free page. If the capacity of the upper tier is insufficent for the allocation, the pages
are allocated to the nearest lower tier. If the capacity of all the tiers is insufficient, an error
message is sent to the host.
If you specify the new page assignment tier to THP V-VOL, the tier to be assigned a new page
can be specified. A default setting for a new page is assigned from the middle tier.
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.
Smart Tiers 83