IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

336 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

Displaying the real-time data of objects and counters is sometimes not enough to identify

server performance. Logged data can provide a better understanding of the server

performance.

Alerts can be configured to notify the user or write the condition to the system event log based

on thresholds.

There are three ways to view the real-time or logged data counters:

򐂰 Chart

This view displays performance counters in response to real-time changes or processes

logged data to build a performance graph.

򐂰 Histogram

This view displays bar graphics for performance counters in response to real-time

changes or logged performance data. It is useful for displaying peak values of the

counters.

򐂰 Report

This view displays only numeric values of objects or counters. It can be used for displaying

real-time activity or displaying logged data results. It is useful for displaying many

counters.

Figure 9-15 The Performance console: System Monitor

9.6.3 Key objects and counters

Performance Monitor provides the ability to monitor many aspects of your system; however,

for our discussion we are interested mainly in I/O-related performance. Table 9-7 on page 337

describes the different I/O-related statistics that can be reported on by Performance Monitor.

Note that some of the statistics require the disk counters that are provided by diskperf.

Chapter 9. Open system servers - Windows 337

The key objects in Windows are:

򐂰 Memory

򐂰 Processor

򐂰 Disk

򐂰 Network

Tuning these key objects will greatly improve the performance of disk I/O.

Table 9-7 Performance monitoring objects

Object Counter Description

Physical disk Percent disk time The percentage of time that a

disk is busy. The general rule is

that the total percent disk time

for all logical disks should be

less than 85 percent.

Physical disks Average disk queue length The number of requests for disk

access. The general rule of

thumb is that the total average

disk queue length should be

less than or equal to three. It

may be important to note the

actual number of spindles in a

hardware RAID set and multiply

the number of spindles by the

average disk queue length.

Logical disks Avg. disk second/transfer The average number of reads

and writes I/Os per second.

Logical disks Disk bytes/second The current reads and writes

throughput per second.

Logical disks Current disk queue length The current number of requests

for access to the logical disk

device.

Cache Copy read hits The percentage of requests

found in the cache. Based on an

analysis of the user

environment the goal was to

emulate approximately an 80

percent cache hit rate.

Memory Cache bytes The amount of the cache

memory currently being used

by the system. The maximum

amount of RAM that the system

can use for caching is 512 MB.

Memory Cache bytes peak Maximum number of bytes

used by the cache at any given

time.