HP XP Array Manager Software - Manual (Page 21)

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.
Note: 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 15.
Workload information mainly displayed by Performance Monitor is as follows:
• I/O rate
The I/O rate indicates how many I/Os are made to the hard disk drive in one second. If the
I/O rate is high, the hosts might consume a lot of time for accessing disks and the response
time might be long.
• Transfer rate
The transfer rate indicates the size of data transferred to the hard disk drive in one second. If the
transfer rate is high, the hosts might consume a lot of time for accessing disks and the response
time might be long.
• The read hit ratio
For a read I/O, when the requested data is already in cache, the operation is classified as a
read hit. For example, if ten read requests have been made from hosts to devices in a given time
period and the read data was already on the cache memory three times out of ten, the read hit
ratio for that time period is 30 percent. A higher read hit ratio implies higher processing speed
because fewer data transfers are made between devices and the cache memory.
• The write hit ratio
For a write I/O, when the requested data is already in cache, the operation is classified as a write
hit. For example, if ten write requests were made from hosts to devices in a given time period and
the write data was already on the cache memory three cases out of ten, the write hit ratio for that
time period is 30 percent. A higher write hit ratio implies higher processing speed because fewer
data transfers are made between devices and the cache memory.
Apart from the items listed above, Performance Monitor also displays additional information about
hard disk drive workloads. For details on how to view workload statistics about hard disk drives, see
“ Monitoring Hard Disk Drives ” on page 61.
Port Traffic Statistics
Performance Monitor tracks host ports and storage system ports to obtain statistics about I/O rates and
transfer rates at these ports. If you analyze these I/O rates and transfer rates, you can determine which
hosts issue a lot of I/O requests to the disk and which hosts transfer a lot of data to the disk. For details
on how to view statistics about traffic at ports, see “ Monitoring Ports ” on page 66.
Note: 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 specified by the user. For
details on the storing period of statistics, see “ Understanding Statistical Storage Ranges ” on page 15.
Note: Performance Monitor can obtain statistics about traffics of ports connected to open-system host
groups only. The statistics about traffics of ports connected to mainframe host groups cannot be obtained.
LU Path Traffic Statistics
Performance Monitor tracks LU paths to obtain statistics about I/O rates and transfer rates at these LU
paths. If you analyze these I/O rates and transfer rates, you can detect LU paths though which a lot
of I/O requests are made to the disk. You can also determine the LU paths through which a lot of
data are transferred to the disk. For details on how to view workload statistics about LU paths, see
“ Monitoring LU Paths ” on page 70.
Note: 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
XP24000 Performance Monitor User's Guide 21