HP XP Array Manager Software - Manual (Page 23)

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 76.
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 82.
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 16.
IMPORTANT:
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 is transferred to the disk. For details on how to view workload statistics about LU paths, see
“
Monitoring LU Paths ” on page 88.
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/XP20000 Performance Monitor User Guide 23