Application and load testing guidelines

  • Last updated on: 2015-11-23
  • Authored by: Lee Kimber

Application and load testing guidelines

Rackspace understands that customers need to determine the performance of their applications and acquire performance benchmarks for their Rackspace-hosted assets as part of offering a professional experience to their own customers. To help Rackspace customers acquire useful data without compromising the performance of their own or other Rackspace customers’ servers, we are providing some helpful load-testing risk indicators.

This article sets out Rackspace’s position on application, load, and performance-benchmarking tests. It also states Rackspace customers’ obligations when performing these tests and provides helpful technical guidance for customers to use when performing these tests.

Note: Customers who perform any testing on or against Rackspace Cloud Servers should be aware that they are operating under the terms of our Global Acceptable Use Policy (AUP).

Policing and enforcement

Rackspace monitors all of our Cloud host servers for activities that reduce the performance of customers’ virtual servers. If we find a customer’s virtual server being used in a way that affects other customers’ virtual servers, we reserve the right to hard reboot, suspend, or switch off the impacting server. We further reserve the right to suspend or terminate the impacting customer’s Rackspace Cloud account.

Customers who want to perform application tests, load tests, and performance-benchmarking tests should observe the following guidelines before and during each test and stop the test immediately if the indicated thresholds are breached.

Load-testing guidelines

Good testing practice requires that you continually monitor the effect of your test as you apply load. Before running such tests, ensure that you know how to view actual RAM, disk IO, and network usage in real-time. These metrics provide the early-warning signs that a test risks interfering with other customers’ servers on the same host. See the following sections for specific thresholds.

Linux virtual servers

Install and use the screen package for your Linux distribution in to run and view the following commands at the same time. To compile screen from source, go to the GNU homepage.

RAM: Use the following command to view RAM use as you perform tests:

 watch free -m

Don’t let the value in the Free column in the +/- buffers/cache line go lower than 1,000.

Disk IO: Use the following command to view disk IO use as you perform tests:


Watch the %wa number in the second line. It might occasionally rise above 1.0 but it should not be above 1.0 for more than a couple of seconds.

Network use: Use the following command to view network use as you perform tests:

 sudo watch -n 10 -d /sbin/ip addr show eth0

Watch the RX bytes number. Every 10 seconds, the -d argument highlights any changes in RX bytes numbers. The 10-second pause gives you time to note the RX bytes number before it changes. You can reduce the amount of math required to calculate exact changes if you remember that at least eight digits must change - per watch -d highlighting - between each 10-second update before you need to apply any arithmetic. For virtual machines with 2 GB RAM or more, at least nine digits must change before you need to calculate the exact change. The following table shows the maximum change in RX bytes per second by server size.

Cloud server size Maximum change in RX bytes per second
512 MB 66,000,000
1 GB 99,000,000
2 GB 198,000,000
4 GB 330,000,000
8 GB 495,000,000
15 GB 660,000,000
30 GB 990,000,000

Windows virtual servers

To view and log the performance of a server, you need to use the Performance Monitor.


This section describes some counters that you can use to ensure that you do not exceed the thresholds and affect other customers on the server. You will have to change the scale of the graphs and also the counters in Performance Monitor, especially regarding memory use. If you find these hard to read and track, we recommend that you use the resmon.exe utility to track them.

Processor use

Counter: Processor Information > % Processor Time > _Total

Purpose: Monitors CPU load as a percentage

Threshold: Don’t let this counter exceed 90 percent.

Memory use

There are several memory-related counters to watch during load testing.

  • Method 1

    Counter: Process > Working Set > _Total (or per specific process)

    Purpose: Shows the current allocated or used RAM by the machine or specific application or process

    Threshold: Don’t let this counter exceed 90 percent of the VM’s total physical RAM.

  • Method 2

    Counter: Paging File > % Usage > Total

    Purpose: Review this value in conjunction with Available Bytes to understand paging activity on your system.

    Threshold: Don’t let this counter rise above 50 percent of total paging size.

  • Method 3

    Counter: Memory > Available MBytes

    Purpose: Free RAM available to be used by new processes, in megabytes

    Threshold: Don’t let this counter fall below 10 percent of total physical RAM.

Note: If you are unsure of the amount of RAM installed, run the msinfo32 command from the Run box.

Disk use

Counter: PhysicalDisk > Disk Time > _Total

Purpose: Amount of time that the disk is active

Threshold: 90 percent

Counter: PhysicalDisk > Avg. Disk Queue Length > _Total

Purpose: Validates the communication medium

Threshold: Don’t let this counter rise above 4.

Network use

Counter: Network Interface > Bytes Total/sec > Network Interface

Purpose: Measures the number of bytes sent or received

Threshold: Don’t let link speed rise above the Maximum PerfMon Link Speed (%) value for your virtual machine’s size as shown in the following table:

Cloud server size Maximum PerfMon Link Speed (%)
512 MB 1.00%
1 GB 1.50%
2 GB 3.00%
4 GB 5.00%
8 GB 7.50%
15 GB 10.00%
30 GB 15.00%

Network latency tests

To remove the network latency-induced components of any remote testing that you perform, you can test the network latency to our various data centers by pinging them and then reviewing the response times or the ping returns. Each Rackspace data center has its own sandbox server that you can use for ping and other network tests. Because most of our Cloud infrastructure is hosted in the same data centers, this test also works for cloud servers.

Ping is publicly accessible for the following servers:


Note: To remove DNS lookup effects, you might want to determine each test server’s IP address and ping the IP address directly.

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