HP XP Array Manager Software - Manual (Page 22)

Access Path Usage Statistics
An access path is a path through which data and commands are transferred within a storage system.
In a storage system, channel adapters control data transfer between hosts and the cache memory.
Disk adapters control data transfer between the cache memory and hard disk drives. Data transfer
does not occur between channel adapters and disk adapters. Data is transferred via the cache switch
(CSW) to the cache memory.
When the hosts issue commands, the commands are transferred via channel adapters to the shared
memory (SM). The content of the shared memory is checked by disk adapters.
Figure 2 Access Paths
.
Performance Monitor tracks and displays the usage rate for the following access paths.
• Paths between channel adapters and the cache switch
• Paths between disk adapters and the cache switch
• Paths between the cache switch and the cache memory
• Paths between channel adapters and the shared memory
• Paths between disk adapters and the shared memory
For details on how to view usage statistics about access paths, see “ Viewing Usage Statistics about
Access Paths ” on page 74.
Hard Disk Drive Workload Statistics
If particular hard disk drives or data are heavily accessed, system performance might deteriorate.
Performance Monitor provides statistics about parity groups and logical devices to help you detect
bottlenecks in your system. If you mapped volumes in an external storage system, Performance Monitor
can also monitor the access workloads of the external volume groups and the external volumes.
Performance Monitor displays a line graph that indicates changes in access workloads, so that you
can detect the peak I/O access times.
You will be unable to view workload statistics that expired a specific storing period because such
statistics are erased from the storage system. The storing period of statistics is only short range (between
8 hours to 15 days) and that changes depending on the collecting interval and the number of CUs
to be monitored specified by the user. For details on the storing period of statistics, see “
Understanding
Statistical Storage Ranges ” on page 16.
Workload information mainly displayed by Performance Monitor is as follows:
• I/O rate
About Performance Monitor 22