3.2 Scalability of the Primary Server

Understanding the scalability of the individual components that make up the ZENworks infrastructure is of the greatest importance. You need to understand the limitations and where you can expect to see performance degradation to ensure that you build an infrastructure that can perform well, regardless of the load that your end-user community places on it.

The first area that you need to consider is the scalability of the Primary Server. It is important to design your Primary Server placement based on the information you collected during your assessment phase and what you anticipate your overall design will require. You should design your infrastructure so that there are always Primary Servers available to service devices and the administrators that are managing the system.

The following sections contain more information:

3.2.1 Factors Influencing Scalability

The main physical factors that govern the scalability of the Primary Servers are:

  • RAM: The majority of operations are performed by two services: zenserver and zenloader. Each of these services can consume approximately 1.2 GB of RAM.

  • Disk I/O: Disk I/O is used when serving content for applications and updates.

The minimum hardware recommendations are listed in Primary Server Requirements in the ZENworks 10 Configuration Management Installation Guide. If you can provide hardware that exceeds these recommendations, your system will perform better. Adding more RAM, however, does not make the specific ZENworks services (zenserver and zenloader) respond more quickly. This is a Java related issue and will be resolved in the future by moving from a 32-bit JVM to 64-bit JVM. If possible, we recommend that you use a 64-bit OS, so that you are ready when this change is made. Additional processing power and faster drives can make the systems more responsive, for example:

  • Using a quad core processor

  • Using 4 GB RAM

  • Allocating as much disk space as you can (RAID 5 with separate physical drives to separate content and ZENworks Configuration Management from the OS)

There are other factors that you need to consider, including:

  • Device refresh frequency

  • Number of Primary Servers being used to deliver content to the managed devices (software, policies, images, patches, inventory collection, and so forth)

  • Number of administrators who have access to ZENworks Control Center

  • Frequency of uploading content in the ZENworks Content Repository

  • Number and frequency of reports run by administrators

3.2.2 Load Testing in the Novell SuperLab

ZENworks Configuration Management is tested in the Novell SuperLab in Provo, Utah to see how much load can be placed on the individual components, and more importantly, where the individual components start to break down and when performance is dramatically affected.

These tests provide insight on how far you can stretch the infrastructure design (for example, how many Primary Servers you need, based on the components and services you plan to deliver).

The following three tests show how Primary Servers react under different loads, and how quickly they can service individual requests when load is increased.

The test included the following hardware and software:

  • A Dell 2950 Dual Quad Core 2.0Ghz, 4 GB RAM, RAID 5 (4 X 300 GB) server was used for the Primary Server.

  • Windows Server 2003 Enterprise on a 64-bit device.

  • ZENworks Configuration Management shipping code.

    • Deploying 100 MB of bundles (11 bundles) to an increasing number of devices.

  • All ZENworks Control Center settings used the default; after the 500-device test, retries were boosted to 800/10/20.

    • Three test passes for each test were run (for example, three test runs with 250 devices).

    • All devices were refreshed “simultaneously” (within 30 seconds).

    • The bundles were chained with the first bundle being associated to a device group set to launch on refresh.

  • All tests were run on a full gigabit network.

The following sections contain more information:

Test 1: Average Time to Refresh

In this test, we used a single ZENworks Primary Server and refreshed all machines inside the lab at the same time. The devices then contacted the Primary Server at approximately the same time. We calculated the amount of time it took for the refresh of the ZENworks Adaptive Agent to complete. As the load increased, the average time increased as well. In fact, the time to complete the refresh increased considerably at the 1,000 device mark. Between 1,000 and 2,000 devices, the amount of time it takes to complete the refresh more than doubled.

The Primary Server scaled well to this point; however, this does not mean that you should implement a single Primary Server to manage 3,000 managed devices. You must always consider the services that are being implemented, and most importantly, fault tolerance and load balancing.

The following graphic shows the average time to refresh managed devices:

Figure 3-1 Average Time to Refresh

Test 2: Average Time to Download

This test demonstrates the results of a download of 100 MB of bundle content, spread across 11 bundles that are chained together. The server load increased as the load (in terms of devices) increased.

The following graphic shows the number of minutes it took to download the content:

Figure 3-2 Average Time to Download

Test 3: Administrative Tasks Performed Under Load

This test used a series of administrative tasks performed on a server with no load and then with a load. These results demonstrate what to expect in a given environment when a certain load is placed on a Primary Server that is multi-tasking. This test provides insight into what you can expect if you do not properly distribute services across multiple Primary Servers. These are conditions that should not exist in a real-world environment; Novell runs these tests to see when the processes begin to break. A well-designed infrastructure should perform well for you regardless of the load you are placing on the servers.

The load consisted of 480 devices running the Daily Use Test.

The Daily Use Test environment in the Super Lab consisted of the following:

  • Single Server: Windows Server 2003 x86_64

  • Server hardware: Dell 2950, Quad Core 2.0 MHz, 8 GB RAM

  • External Microsoft SQL Server 2005 database

Definition of the “Daily Use” included the following:

  • 24-hour period simulated in four hours

  • Three bundle pushes of 105 chained bundles (30 MB to 1 KB) per device

  • One full and three delta inventory scans per device

  • One patch distribution per device

  • Four device refreshes per device

  • Ten devices continually restoring images

This test environment stretched the limits of what the ZENworks Configuration Management system is able to achieve, giving us a good idea of where the system starts to reach its limitations. It comes close to a real-world simulation.

Table 3-1 Tests and results.

Test Name

Test Description

Primary Server Under No Load

Primary Server Under Load

BOE Report

Run Predefined BOE report - Bundle Deployment Status (313 pages)

15 seconds

18 seconds

Inventory Report

Run canned report “Devices By Machine / Login Name”

7 seconds

8 seconds


Create policy, assign it to 60 devices, and perform a quicktask on all 60 devices to get the policy

7 minutes 43 seconds

7 minutes 45 seconds


Create Multicast bundle and multicast to 60 devices

4 minutes 20 seconds

4 minutes 27 seconds


Create an MSI Bundle of OpenOffice, assign it to 60 devices, and refresh all 60 by using a quicktask

25 minutes 30 seconds

1 hour 10 minutes 17 seconds

When the server is under load, and we created an MSI bundle and assigned it to 60 devices, there is a large increase in the amount of time it takes to complete the task. In this situation, it is recommended that you have a dedicated server for ZENworks Control Center so that there would be virtually no impact on performance.

The ZENworks Control Center is used by administrators to perform administrative tasks, including the management of content within the system. For environments that are managed by a small number of administrators (one or two), accessing ZENworks Control Center from a Primary Server that is also performing work might not be cause performance issue. For larger implementations (several thousand devices, large amounts of daily content activity, and several administrators), having a dedicated Primary Server in place for ZENworks Control Center resolves potential performance issues.

3.2.3 Achieving Scalability in the Real World

Section 3.2.2, Load Testing in the Novell SuperLab discussed testing in the Novell SuperLab to determine the limits of the ZENworks system. Scalability, on the other hand, is achieved through the proper placement of services, a well thought-out design, and the proper configuration of services within the ZENworks Configuration Management system itself.

For example, even though we know that a Primary Server can manage 3,000 devices, you should never deploy only one Primary Server in a 3,000-device environment. For this situation, we recommend the following as a starting point:

  • Three Primary Servers to manage load and build a system that is fault tolerant.

  • A dedicated Database Server using Sybase, Oracle, or Microsoft SQL Server.

This system should be further enhanced by considering the following:

  • Using an L4 switch to manage fault tolerance and load balancing.

  • Using DNS and aliases for managing the load placed on Primary Servers during deployment and registration.

  • Using custom Closest Server Rules to designate certain servers for specific functions (content, collection, etc.) and to exclude servers from specific functions, or all functions. If a Primary Server is not listed in the Closest Server Rules, then it does not perform the functions.

  • Using a dedicated Primary Server for reporting.

  • Using a dedicated Primary Server for Patch Management.

  • Using a dedicated Primary Server for imaging.

  • Using a dedicated Primary Server for ZENworks Control Center.

  • Using Satellite devices for distribution of content.

The Primary Servers are the heart of your ZENworks Configuration Management environment. You want to protect these systems from major disruption. Primary Servers can be used for distribution of content, but this needs to be factored in to your design.

Some of the major factors that you need to consider with ZENworks Configuration Management and Primary Servers are the following:

  • Each Primary Server can comfortably handle 1,000 concurrent connections.

  • Each Primary Server can manage 3,000 devices that are registered into the ZENworks Management Zone.

  • A ZENworks Management Zone can scale to 40,000 devices. This has been validated in the SuperLab and is what Novell recommends as the upper limit to the Management Zone size.

We also recommend that Primary Servers and the Database Server be on the same network, in the same data center. We do not recommend spanning WAN links with Primary Servers because replication of the Content Repository could cause utilization issues. Placement of services in a multi-site environment is done by utilizing the Satellite role, which is discussed in more detail in the next section.