Table of Contents
Advertisement
Chapter 1 Overview of Performance Monitoring Function
(1) Monitored Items
Monitored items are types of index values which indicate status of load or performance. iSM displays values of the
following types of monitored items on the client screen.
(i)
External I/O Density
This is the number of input/output requests received by the disk array from the external per unit time. The unit is
IOPS (Input Output Per Second). This is calculated by measuring the external I/O count during the unit
measurement period and dividing it by the time interval of the measurement period.
(ii)
External Transfer Rate
This is the Average Transfer Rate of the input/output process achieved in response to the input/output requests
received by the disk array from the external. The unit is megabyte/second. This is calculated by measuring the
total of the amount of external data transfer during the unit measurement period and dividing it by the time interval of
the measurement period.
(iii) External Average Transfer Length
This is the average input/output data length per one input/output request received by the disk array from the external.
The unit is kilobyte. This is calculated by measuring the total of the amount of external data transfer and external I/O
count during the unit measurement period and dividing the former by the latter.
(iv) External Average Response Time
This is the Average Response Time for the input/output requests received by the disk array from the external. The
unit is millisecond. This is calculated by measuring the total of the external response time and external I/O count
during the unit measurement period and dividing the former by the latter.
(v)
Busy Ratio
It is the ratio of operation of physical disk. The unit is percentage [%]. It is calculated by following expression;
dividing the operating time of physical disk by the time slot of measured segments.
(vi) Read Hit Ratio
It is the ratio of case where the READ request has been completed using data stored in the cache without reading from
physical disk (Read hit), when the disk array receives the input requests from outside. The unit is percentage [%]. It
is calculated by following expression; dividing the number of cache hit I/Os by the number of receiving READ
requests during the measuring interval.
(vii) Write Hit Ratio
This is the ratio of case where the WRITE request has been completed quickly by writing data only in the cache
(Write hit), when the disk array receives the output requests from outside. The unit is percentage [%]. It is calculated
by following expression; dividing the number of cache hit I/Os by the number of receiving WRITE requests during the
measuring interval.
(viii) Internal I/O Density
This is the number of input/output requests issued to the internal disk devices by the control device of the disk array.
The unit is IOPS (Input Output Per Second). This is calculated by measuring the internal I/O count during the unit
measurement period and dividing it by the time interval of the measurement period.
(ix) Internal Transfer Rate
This is the average transfer rate of the input/output requests issued to the internal disk devices by the control device of
the disk array. The unit is megabyte/second. This is calculated by measuring the total of the amount of internal
I-8
Advertisement
Table of Contents
