HP XP7 Storage User Manual
Page 72
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. Normally, a free page is selected for allocation from an upper
tier with a free page. If the capacity of the upper tier is insufficient for the allocation, the pages
are allocated to the nearest lower tier. A THP V-VOL set to a tier policy is assigned a new
page that is based on the tier policy setting. The relative tier for new page allocations can be
specified during operations to create and edit LDEVs. If the capacity of all the tiers is insufficient,
an error message (SIM=622xxx) 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 View Tier Properties window
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.
Monitoring mode settings (see
) of Period or Continuous
influences the values shown on the performance graph. Period mode will report the most recent
completed monitor cycle I/O data on the performance graph. Continuous mode will report a
weighted average of I/O data that uses recent monitor cycle data, along with historical data
on the performance graph.
72
Configuring thin provisioning