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Understanding Client Access and Hub Transport Combined Role Configurations in Capacity Planning

Exchange 2010
 

Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2

Topic Last Modified: 2010-09-21

A common trend in server hardware is a significant increase in processor performance and an increasing number of processor cores supported on a physical processor. This means that deploying a single Exchange server role on a standard commodity server with two physical processors may leave a portion of available CPU underutilized. Some customers expect server virtualization to more effectively use server CPU resources. Other customers want to combine Exchange server roles on the same physical server. Both can be valid solutions if implemented according to deployment recommendations and best practices.

You can use the information in this topic to help determine when you should deploy the Client Access server role and the Hub Transport server role on the same physical server, and how to properly plan for the combined role configuration. For information about deploying the Client Access, Hub Transport, and Mailbox server roles on the same physical server, see Understanding Multiple Server Role Configurations in Capacity Planning.

Contents

When Client Access and Hub Transport Combined Role Configurations Are Recommended

Processor Recommendations for Client Access and Hub Transport Combined Role Servers

Client Access and Hub Transport Combined Role Server Configuration Alignment with Recommended Processor Core Ratios

Memory Recommendations for Client Access and Hub Transport Combined Role Servers

Determining Client Access and Hub Transport Combined Role Server Hardware Requirements

Client Access and Hub Transport Combined Role Servers and Virtualization

We recommend that you deploy the Client Access and Hub Transport server roles on the same physical server if you're considering the following:

  • Server consolidation   For deployments where the primary goals are to minimize the number of physical servers, operating system instances, and Exchange servers to manage, a Client Access and Hub Transport combined role deployment is a recommended solution. Running the Client Access and Hub Transport server roles on the same physical server provides the necessary role redundancy with a minimum requirement of two physical servers.

  • Virtualization   For deployments where virtualization host servers have processor counts divisible by 8 (8, 16, 24, 32, or 48), deploying Client Access and Hub Transport combined role servers in a 1:1 processor core ratio with single role Mailbox servers ensures a well-balanced virtual machine placement regardless of host server size.

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The maximum recommended processor core configuration is 12 processor cores for the Client Access and Hub Transport combined role servers. Although the Client Access and Hub Transport combined role configuration can be deployed on servers with more than 12 processor cores, we don't recommend it.

The following describes the minimum requirements and recommended maximum configurations:

  • Minimum   This is the minimum processor and memory configuration suitable for the Client Access and Hub Transport combined role server. The minimum hardware requirements must be met to receive support from Microsoft Customer Service and Support.

  • Recommended maximum   This is the maximum recommended processor and memory configuration for the Client Access and Hub Transport combined role server. Recommended maximum is defined as the upper limit of viable processor and memory configurations based on price and performance. The recommended maximum configuration is a guideline. It isn't a support criterion, and it doesn't include the resource requirements of third-party applications that might access or be installed on the server. The recommended maximum configuration may change over time based on price changes and technology advancements.

The following table shows the minimum and recommended maximum processor cores for Microsoft Exchange Server 2010 combined role servers.

Processor configurations for Exchange 2010 Client Access and Hub Transport combined role servers

Exchange 2010 server role Minimum Recommended maximum

Client Access and Hub Transport combined role servers

2 x processor cores

12 x processor cores

importantImportant:
Some server virtualization platforms may not support the maximum number of processors identified in the table above. If you're planning to deploy Exchange server roles on a virtualization platform, please check the documentation for that platform to determine the maximum number of supported virtual processors.

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The following table outlines the recommended number of processor cores deployed for the Client Access and Hub Transport server roles relative to the number of processor cores deployed for the Mailbox server role. The standard core ratios don't align well to the number of processor cores available on systems today. Unless you have a large organization with many Client Access, Hub Transport, and Mailbox servers, your deployment probably won't match the desired processor core ratios.

Client Access and Hub Transport combined role server configurations can solve this problem and should result in more optimal hardware utilization. For example, if you have a server with four processor cores, the Client Access server role uses approximately three cores, and the Hub Transport server role uses approximately one core. If you deploy this in combination with four core Mailbox servers, the result is a 4:1 Mailbox to Hub Transport server role core ratio and a 4:3 Mailbox to Client Access server role core ratio. This closely aligns with the recommended processor core ratio guidance.

The following table shows the recommended server role ratios based on processor core for combined role servers.

Processor configurations for Exchange 2010 Client Access and Hub Transport combined role servers

Server role ratio Recommended processor core ratio

Mailbox:Hub Transport

7:1 (with no antivirus application scanning on the Hub Transport server)

5:1 (with an antivirus application scanning on the Hub Transport server)

Mailbox:Client Access

4:3

Mailbox:Client Access and Hub Transport combined role server

1:1

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The following table illustrates the minimum and recommended maximum memory configurations for Exchange 2010 combined role server configurations.

Memory configuration for Exchange 2010 combined role servers

Exchange 2010 server role Minimum Recommended maximum

Client Access and Hub Transport combined role servers

4 GB

2 GB per core

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To determine the hardware requirements for the Client Access and Hub Transport combined role server, you first need to determine the hardware requirements for the Mailbox server role. For more information, see Mailbox Server Processor Capacity Planning.

Use the number of processor cores that will be deployed for the Mailbox server role and deploy an equal number of processor cores for the Client Access and Hub Transport combined role server. For example, for every Mailbox server with eight processor cores, deploy a Client Access and Hub Transport combined role server with eight processor cores. Then apply memory configuration guidelines to the processor core count. For example, if your Client Access and Hub Transport combined role server has eight processor cores, you will need 2 GB per core or 16 GB of memory per server.

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If you plan to virtualize Exchange, using Client Access and Hub Transport combined role servers can make the planning process easier. The recommended sizing for virtual machines is summarized in the following table.

Recommended sizing for virtual machines for Exchange 2010 Client Access and Hub Transport combined role servers

Virtual machine role Recommended number of virtual processors Recommended memory

Client Access and Hub Transport combined role servers

4 x processor core

8 GB

Mailbox server role

4 x processor core

4 GB plus 3-30 megabytes (MBs) per mailbox.

This variable is based on the user profile. For details, see "Recommended Memory Configurations" in Understanding Memory Configurations and Exchange Performance.

noteNote:
Not all server virtualization platforms support the same number of maximum virtual processors. If you plan to deploy Exchange server roles on a virtualization platform, check the documentation for that platform to determine the maximum number of supported virtual processors.

We recommend that you deploy these virtual machines in a 1:1 ratio (for example, deploy one Client Access and Hub Transport combined role virtual machine for every Mailbox server role virtual machine).

If you're using virtualization servers dedicated to hosting Exchange virtual machines and the processor core count is divisible by 8 (8, 16, 24, 32, or 48), placement of virtual machines is straightforward. For example, if your virtualization root server has eight processor cores, deploy one Client Access and Hub Transport combined role virtual machine and one Mailbox server role virtual machine. If your virtualization root server has 16 processor cores, deploy two of each. If your root server has 24 cores, deploy 3 of each, as shown in the following figure.

Virtualization servers

Virtual machines recommended sizing example

With this design, you can maintain Exchange role redundancy across root servers and balance Exchange workloads for effective utilization of root server resources. The following table provides a summary of recommended sizing guidance for root servers hosting Client Access and Hub Transport combined role virtual machines.

Recommended sizing for virtual machines for Exchange 2010 Client Access and Hub Transport combined role servers

Root server processor cores (root servers with 12 x processor cores don't fit this model) Root server memory requirements Recommended memory configuration Number of Client Access and Hub Transport combined role virtual machines Number of Mailbox server role virtual machines

8

26 - 34 GB

32 GB

1

1

16

53 - 69 GB

64  GB

2

2

24

76 - 100 GB

96 GB

3

3

32

131 - 143 GB

160 GB

4

4

48

152 - 200 GB

192 GB

6

6

noteNote:
Root server memory recommendations are based on root operating system requirements, plus virtual machine requirements. Mailbox virtual machine requirements are dependent on mailbox profiles. For more information, see "Recommended Memory Configurations" in Understanding Memory Configurations and Exchange Performance.
noteNote:
Costs should be considered when purchasing memory. You may have to reduce the number of active mailboxes hosted on each Mailbox server virtual machine to align root server memory requirements with the purchased memory configuration.

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