NEC Storage Performance Monitor/Optimizer User Manual page 10

Chapter 1 Overview of Performance Monitoring Function
Reviewing cause of overload
Display performance information on the real-time basis and check
location of overload. Then, analyze the accumulated statistic
information to determine the cause of the overload.
Analysis of statistic information makes it possible to improve
performance as shown in the examples provided below.
• If there is a problem with the file arrangement and the access load
concentrates in a specific logical disk, the I/O density of the logical
disk should be higher than that of other logical disks and its response
time should be longer. If this is the case, it is necessary to review
the file arrangement and distribute the load.
• If a write operation onto the disk is slow, the cache size is
insufficient. A write operation onto physical disks may be
simultaneously performed. This status is confirmed by checking to
see if the Write Hit ratio is less than 100%. If this is the case, it is
recommended that the cache size of the disk array be expanded.
• If response is not quick although the access density from the business
server to the logical disk is low, the access density to another logical
disk on the same RANK may be high. This state is confirmed by
the fact that the Busy Ratio of the RANK is high. If this is the case,
use the performance optimization function described in Part II to
move the logical disk, which has the high access density, to another
RANK and level out the Busy Ratio of each RANK. On the other
hand, reviewing the processes of a business application to reduce
access operations to a disk or improving access efficiency by batch
accessing can be good solutions to some cases.
Improving performance
Displaying statistic information on a
real-time basis
1.5.1 Real-Time Display of Load State
3.1 Real-Time Display of Load State
Analyzing statistic information
1.5.3 Analysis support for statistic
information
3.3 Support for Analysis of
Statistic Information
A.1 Commands for Statistic
Information File
Against high busy ratio on RANK:
Part II Performance Optimization
Function
I-4