Performance Testing and Load Balancing

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(For more resources related to this topic, see here.)

Initial and on-going performance measurement

Performance measurements begin prior to system deployment. In terms of a failover cluster of Hyper-V systems, it begins prior to creating any virtual machines. Your first goal is to obtain baselines. The term baseline has different meanings in different contexts; in this case it means gathering data on a system during a known healthy period. Its purpose is to serve as a point of comparison for later data gathering operations.

The first set of performance measurements you take will be with no virtual machines. Once you have reached your target deployment level, you will obtain another. These will be your baselines. All future performance measurements will be compared to these in order to determine how your systems are working.

Microsoft provides a thorough document for performance tuning of Windows Server 2012. These concepts carry forward to R2 and many apply to Hyper-V Server as well. Download it from the following site:

General performance measurement

Baselines and ongoing performance evaluations tend to be fairly generic in nature. They can be carried out in a number of ways. This section will examine two others. The first is the free Server Performance Advisor ( SPA ) provided by Microsoft. The second is the Performance Monitor tool in-built in Windows operating systems.

Server Performance Advisor

This tool can be run quickly to determine the performance characteristics of a new system and on a schedule to track the performance trends of an active system.

Do not install or run Server Performance Advisor directly on a Hyper-V host or any guests that are to be measured. Doing so adds a load that will make the results inaccurate.

The following instructions can be used to quickly set up SPA to run in a basic environment. They assume that you’ll be running the application with a domain account that has administrative privileges on the systems to be measured. To scan a system that has an active firewall, run the following cmdlet:

Enable-NetFirewallRule -DisplayName "Performance Logs and Alerts (TCP‑In)"

Service Performance Advisor is published on the developer center, which is accessible at For best results, this tool should be run from a remote computer that’s not on the host being measured. It can be run from any modern Windows system. It requires a connection to an installation of Microsoft SQL Server 2008 R2 or newer. The Express edition is perfectly acceptable. The latest version can be obtained at no charge from the Microsoft download center at

There is another requirement that’s listed on the download page but not in the included documentation. The CAB file that SPA is delivered in must be extracted with its directory structure intact. If you use Windows Explorer to open the CAB, it will not extract the files properly. Use the built-in extrac32 tool according to the directions (they’re on the download page) or use another extraction application that can reproduce the proper folder structure.

The final prerequisite you must satisfy is the creation of a folder to hold the results. This folder can be in any location on the system you’ll be running SPA from, and it can have any name. This folder must be shared. Determine the domain account that you’ll be running SPA with and give that account full permissions to the folder and its share.

All that’s left is to run SPA. In the folder where you extracted the CAB’s contents, run SPAConsole.exe. When it opens, choose File and then New Project to get started. The first screen is just a basic introductory screen. Click on Next and you’ll see the following screen, which has been filled in with examples:

The previous entries direct the application to create a database on the local computer, in this case an instance of SQL Server Express. For a large environment with many systems to scan, it is recommended to use SQL Server Standard instead. The database name can be anything you like; this one has been named to reflect that it will contain data on the first Hyper-V cluster in the sample organization. Be aware that this will create a new database on the selected server. Once you have selected the database server, instance, and name, and then click on Next to move to the following screen:

This screen allows you to select the advisor packs that you’d like to make available in this project. Even though you only need the Hyper-V advisor and perhaps the CoreOS advisor, it’s best to select all three. The interface sometimes hangs if only a subset is selected. You won’t be required to use all three during a scan. Click Next . This will bring you to the final screen:

On this screen, enter the servers that you want to scan. The File Share Location is a file share that will hold the results of the scan. As with the SQL database, it’s not required to be on the same system as the scanner. Servers can be added to the list later. You can use Test Configuration to ensure that the indicated servers are reachable. Once you’re happy with the entries, click on Finish .

You’ll be returned to the main screen of SPA. Now, you should see the host(s) that you selected for this project. Select their checkboxes, and then press the Run Analysis button in the lower-right corner. Here, you’ll be able to select the actual advisor packs that you want to use. At the bottom of the screen, you’ll be able to enter how long you want the scan to run, and if you wish to collect numerous data points over a period of time—how often you want it to run. Click on OK when you’re satisfied with your selections and the data collection process will begin.

Once it is complete, you can click on the small down arrow in the Analysis Result column of one of the hosts. This will show three buttons, indicated in the following screenshot:

These buttons are, from left to right:

  • View Latest Report : See the report from the latest analysis. This is the screen you’re most likely to be interested in after a one-time scan of a new system. It will show warnings for any items and settings it finds that might impede optimal performance of Hyper-V. It can also compare one report against another and export result sets to XML.
  • Find Reports : Search through all result sets for this host according to the criteria that you choose.
  • View Charts : These are detailed charts that examine and graph very specific performance metrics of the host.

    The wording of the Logical Processor count limit when Hyper-V is enabled warning is misleading. The management operating system is restricted to using 64 logical processors, but Hyper-V itself can still schedule guest processes up to the maximum of 320 logical processors.

The first two buttons are very simple to understand and you should have no trouble navigating them on your own. Do remember to check the various tabs inside the report. The third button, View Charts , brings you to a tool that isn’t as easy to decipher. You’ll begin by picking a range of dates, and assuming that you’ve got more than one report to chart, you’ll get a screen that looks something like the following screenshot:

The sheer amount of data shown can make this difficult to interpret. In the lower section, you’ll notice that there is a large number of performance counters. Select only those that you’re actually interested in viewing and you’ll find that the chart becomes much easier to understand. To deselect all items, select the first item and press Ctrl + A , and then press the Space bar.

The items marked as 90% remove all utilization above the 90 percent mark. These are assumed to be momentary spikes that can skew the outcome in a way that makes the data meaningless. Compare these to the same metrics marked as Max .

Use the Pick Series button at the bottom of the window if you wish to reduce the number of selectable items. This button is more useful on the other two tabs; in fact, they’ll have no data to display if you do not select an item. As indicated, these two tabs show the way that the selected metrics have been trending over a specified period of time. These can show you how your systems behave differently during the day or across a week. Comparing these reports against those generated by other servers can help you to determine how your guests should be load balanced.

Performance Monitor

The built-in Performance Monitor tool is much more powerful than most others; but it’s up to you to choose what to measure. One of its major strengths is that there’s nothing to install. All you need is a Windows system with a GUI.

As with Server Performance Advisor, it is not recommended that you run this on a Hyper-V host or guest that you are going to measure.

There are two ways to run Performance Monitor. One is as a real-time tool that graphs the monitored performance counters as they occur. The second is as a collector that gathers metrics and stores them for trend analysis. The differentiating features of Performance Monitor from Server Performance Advisor are:

  • Real-time graphing
  • Precise selection of metrics
  • No software downloads required
  • No database system required
  • Performance logs can be opened on any Windows system

Performance Monitor is found in Administrative Tools. Depending on how your system is configured, Administrative Tools may be found on the Start screen or menu. It’s available in the Control Panel in all versions of Windows. It’s also available under the Performance node of Computer Management . If you will be running it for real-time graphing, ensure that you start it with an account that has administrative privileges on the target system. For collectors, you’ll be able to specify the account to run it under. You may also need to modify the firewall as indicated under the Server Performance Advisor section mentioned earlier.

Real-time monitoring with Performance Monitor

To start a real-time monitoring session, expand the Monitoring Tools node and click on Performance Monitor . In the center pane, click on the button with the green plus, which will open the Add Counters window. In this window, you’ll want to change the counters’ source to the target computer. Your screen should look like the following screenshot:

Navigate through the various counters in the upper list box. When you click on one, it will show the instances of that counter that are available to be monitored. Double-click on an instance or highlight it and click on the Add >> button to move it to the list box on the right. These are the objects that will be tracked. When you are satisfied with your selection, click on OK . See Step 4 in the next section for a screenshot of this window and more information about its contents.

You will be returned to the main screen. The display will be updated every second. Each counter you picked will be displayed as a line of a various color. The legend will be shown at the bottom. You can uncheck an item to hide it from the running display; however, its counter will still be monitored.

Using the buttons across the top of the graph pane, you can modify the output. Most of the options are self-explanatory; change them until the display suits your desires. You have the ability to modify the graph from its default line output to a histogram or to a running digital display. Click on the Highlight button and then select a counter to make it stand out against the others. Several of the buttons open various tabs on the Performance Monitor Properties window where you can change many settings, such as the delay between samples. Of interest here is the Source tab, which will be used in the next section.

Trend tracking with Performance Monitor

The second use for Performance Monitor is to pull performance statistics across a span of time. In active deployments, it can be used to track the performance of Hyper-V hosts. You’ll create scheduled gathering of data collector sets for this. What makes Performance Monitor especially useful for this is that a single collector set can gather from all the hosts in your cluster simultaneously.

Before you start, ensure that the Performance Monitor console is not connected to the target computer system as it would be for a real-time monitor. For instance, if you are using Computer Management as shown in the first screenshot in this article, the tree root should say Computer Management (Local) and not contain the name of another system. The first reason is that running and managing the collector sets creates a small drain on the system’s resources. Second, you’re going to be running collectors against multiple systems and it’s better to use a single remote computer for those purposes. Third, it’s easiest to look at the results of performance logs on the system that took them. Otherwise, you have to move them around.

Look under the Data Collector Sets tree item. There are a number of predefined collector sets and you can add more. Just right-click on the User Defined node and choose New and Data Collector Set. The following steps will take you through the creation of a collector set:

  1. On the first screen, come up with a name for the set, then choose to manually create the set, then click on Next :

    This wizard will create a data collector named DataCollector01 which cannot be renamed. If you wish, you can skip through the wizard to the end, delete the generic collector, and then create new ones with friendlier names.

  2. On the second screen, you want to create performance counter data logs:

  3. On the third screen, you can change how often the collector polls for data. As you can see in the following screenshot, the default is every 15 seconds:

  4. Click on the Add… button in the previous screen to pick the counters that you want to poll. This is the same screen that you see when selecting counters in the real-time screen. Enter the name of the computer you want to poll data from in the Select counters from computer text box. Upon pressing Tab or Enter or clicking on another control, it will load the counters from that system. Select the counters and instances that you desire and click on Add >> . You can monitor counters from multiple computer systems in the same collector set if you like, but you may also choose to use one collector per computer per set. Remember that you’ll want to select Hyper-V related counters for CPU, memory, and networking or you’ll be retrieving collectors from the parent partition only. Physical disk counters are read from the management operating system.

    You cannot retrieve statistics for pass-through disks by setting performance counters on the management operating system.

  5. If you click on the Add >> button and nothing happens, it is because instances are required but didn’t load. Click on another counter and then back on the desired counter until the instances are displayed.

  6. On clicking OK , you’ll be returned to the previous screen that will now be populated with the counters that you chose. Ensure everything looks as you wish and click on Next .
  7. You’ll now be asked for a location to save the logs to. Although it will allow you to enter a UNC, logfile creation is usually unsuccessful anywhere but on the local system. You may place them in a local folder that is shared for easy accessibility from other systems, if you wish.

  8. The final screen will have you provide the credentials that the set will use. If you leave it on its default setting, it will use the Local System account that will not have the necessary rights to run the collection on the target computer. You have two choices: you can add the computer account of the collector machine to the Performance Log Users group on all target machines or you can use an account that is a member of that group on all machines. For the purposes of this step-through, we’re just going to use the domain administrator account:

  9. Before clicking on Finish , you are encouraged to set the radio button to Open properties for this data collector set . This will allow you to jump straight to the properties window where you can schedule the scan. Alternately, you can open the properties window by right-clicking on the completed collector set and clicking on Properties .
  10. In the properties window, change the options as you like. The Schedule tab is where you establish the Start and End times. You can create multiple schedules for a collector set:

  11. If you want to use a separate collector in this set for another host, right-click on the new Collector Set in the left pane and click on New and Data Collector . The wizard is very nearly identical to the one you just completed.

You aren’t required to follow a schedule. You can manually start and stop collector sets by right-clicking on the menu in the left pane.

Once the collector has begun its work, you can go back to the real-time monitor screen and open the Performance Monitor Properties window to the Source tab. Select the logfile that you instructed the collector set to use. The display will switch to the static output of the logfile. However, it will be blank because by default, no counters are selected. Add counters with the green plus button just as you did with the real-time display. This time, you’ll only be able to choose from counters that are contained in the logfiles. You can now manipulate the log contents as you did with the live display. Note that you can view a log of an actively running collector, but the screen will not update in real time.

Selecting counters practically

If you use the exact counters as shown in the example, you’ll notice that some of them aren’t very useful. For instance, the number of processors in a host is highly unlikely to change during a monitoring session, although the number of virtual processors might. Not all of the available counters are well documented, but there is a Show description check box on the counter selection screen that provides a bit of information. Also, some of the counters you can pull don’t compare well from one host to another. In the sample, we instructed SV-HYPERV1 to monitor the amount of data traveling across the virtual adapter in SV-DC1. This is useful data in its own right, but probably in isolation, not as a comparator. Of course, if the virtual machine migrates to another host, it will no longer be readable. You may find the aggregate counters to be more useful than specific virtual machine counters.

The counters that are truly useful are simply too numerous to make a meaningful list out of, and not all counters are universally useful in all organizations. The four generic categories you’re likely to be interested in are CPU, disk, memory, and networking. Be judicious about selecting counters that look at specific highly available virtual machines.

Alternative ways to read performance logs

Performance logs can be confusing, especially when you first encounter them. There are a number of tools on the market designed to aid you. One free and popular tool is the Performance Analysis of Logs ( PAL ) Tool. It is a free and open source tool downloadable from Codeplex at


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