1. Analyzing Processor Usage
Most often, the processor resource is the
first one analyzed when system performance decreases noticeably. For
capacity-analysis purposes, you should monitor two counters: %
Processor Time and Interrupts/sec.
The % Processor Time counter indicates the
percentage of overall processor utilization. If the system has more
than one processor, an instance for each one is included along with a
total (combined) value counter. If this counter averages a usage rate
of 50% or greater for long durations, you should first consult other
system counters to identify any processes that might be improperly
using the processors or consider upgrading the processor or processors.
Generally speaking, consistent utilization in the 50% range doesn’t
necessarily adversely affect how the system handles given workloads.
When the average processor utilization spills over the 65% or higher
range, performance might become intolerable. If you have multiple
processors installed in the system, use the % Total Processor Time
counter to determine the average usage of all processors.
The Interrupts/sec counter is also a good
guide of processor health. It indicates the number of device interrupts
that the processor (either hardware or software driven) is handling per
second.
Conditions that could indicate a processor bottleneck include the following:
• Average of % Processor Time is
consistently over 60% to 70%. In addition, spikes that occur frequently
at 90% or greater could also indicate a bottleneck even if the average
drops below the 60% to 70% mark.
• Maximum of % Processor Time is consistently over 90%.
• Average of the System Performance Counter; Context Switches/second is consistently over 20,000.
• The System Performance Counter; Processor Queue Length is consistently greater than 2.
By default, the CPU tab in Resource Monitor, shown in Figure 1,
provides a good high-level view of current processor activity. For more
advanced monitoring of processors, use the Performance Monitor snap-in
with the counters discussed previously.
Figure 1. CPU section of the Resource Monitor.
2. Evaluating the Disk Subsystem
Hard disk drives and hard disk controllers
are the two main components of the disk subsystem. The two objects that
gauge hard disk performance are Physical and Logical Disk. Although the
disk subsystem components are becoming more and more powerful, they are
often a common bottleneck because their speeds are exponentially slower
than other resources. The effects, though, can be minimal and maybe
even unnoticeable, depending on the system configuration.
To support the Resource Monitor’s Disk
section, the physical and logical disk counters are enabled by default
in Windows Server 2012. The Disk section in Resource Monitor, shown in Figure 2,
provides a good high-level view of current physical and logical disk
activity (combined). For more advanced monitoring of disk activity, use
the Performance Monitor component with the desired counters found in
the Physical Disk and Logical Disk sections.
Figure 2. Disk section of the Resource Monitor.
Monitoring with the Physical and Logical Disk
objects does come with a small price. Each object requires a little
resource overhead when you use them for monitoring. As a result, you
might want to keep them disabled unless you are going to use them for
monitoring purposes.
So, what specific disk subsystem
counters should be monitored? The most informative counters for the
disk subsystem are % Disk Time and Avg. Disk Queue Length. The % Disk
Time counter monitors the time that the selected physical or logical
drive spends servicing read and write requests. The Avg. Disk Queue
Length monitors the number of requests not yet serviced on the physical
or logical drive. The Avg. Disk Queue length value is an interval
average; it is a mathematical representation of the number of delays
the drive is experiencing. If the delay is frequently greater than 2,
the disks are not equipped to service the workload and delays in
performance might occur.
