Exchange 2007: Use Roles When Right-sizing Server Hardware

Exchange 2007: Use Roles When Right-sizing Server Hardware

Date: June 12, 2007

Exchange Server 2007 represents a complete re-envisioning of enterprise e-messaging for the Microsoft platform. Server roles play a central part. Use these guidelines to right-size server hardware and plan enterprise deployment.

One Actor, Five Roles

Exchange Server 2007 parses core messaging functions into five roles. Begin by understanding the roles and their functions.

·         Client Access Server. This role answers all non-MAPI access requests such as those made via Outlook Web Access, Exchange ActiveSync, POP3, and IMAP. The Exchange ActiveSync Direct Push feature automatically synchronizes data to mobile devices (forwarding e-mail, for example), but will only work with cellular devices, not over Wi-Fi. When implemented in a redundant architecture, the Client Access Server role can also perform load-balancing.

o    Do not confuse this role with the front-end server for Exchange 2003. The Client Access Server off-loads significant processing tasks from the Mailbox Server including Exchange ActiveSync policies and Outlook Web Access (OWA) segmentation.

·         Edge Transport Server. Residing in a DMZ with only limited access to the organization’s Active Directory (AD), this server directs mail flow, enforces policies and compliance, and performs anti-virus/anti-spam functions before passing mail to the Hub Transport Server.

o    The Edge Transport Server’s Address Rewriting feature allows an organization to modify all out-going messages to present the same, corporate e-mail domain name. Conversely, address rewriting can be used to modify incoming e-mail messages to route them to specific domain-names. This will be most useful to enterprises comprised of multiple subsidiaries.

·         Hub Transport Server. The Hub Transport Server role directs mail flow within the organization and enforces transport rules and journal rules (which allow e-mail to be recorded by the enterprise). Multiple Hub Transport Server roles can be implemented in a redundant architecture for load-balancing.

·         Mailbox Server. This role stores all mail, interacts with all other roles to fulfill retrieval requests, handles MAPI-based Outlook requests, and manages Contacts, Public Folders, and Distribution Groups.

·         Unified Messaging Server. Voice and fax messaging are integrated into the user’s inbox. The Unified Messaging Server role can answer the telephones, route VoIP traffic, receive faxes, and interoperate with third party fax server software to send faxes.

At a minimum, enterprises will want to use three servers:

1. An Edge Transport server in a DMZ.
2. A standalone Unified Messaging server.
3. A combined Client Access, Hub Transport, and Mailbox Server.

See the recommendations below for how many Mailbox Servers the enterprise will require. Larger enterprises will also add additional Client Access and Hub Transport Servers to perform load-balancing.

Recommendations

Microsoft offers plenty of material to help shops size the servers and suggest possible architectures based on messaging load. Here are the highlights:

1. General Guidance.
   • Hardware. Provide 2 processor cores and 2GB of RAM on each Exchange Server 2007 role server. Allocate at least 1 GB of RAM for each additional processor core (except Mailbox Server, which has heavier requirements).
   • Network Architecture. Install the Client Access Server first. The Hub Transport Server, Mailbox Server, and Unified Messaging Server must be installed in this order. The Edge Transport Server can be installed anytime after the Client Access Server.
   • Combining Roles. When two roles are combined (e.g. Client Access and Hub Transport) into one physical server, plan for a 20% reduction in capacity.
   • Virtualization. Exchange 2007 roles can be virtualized. Currently, Microsoft’s Virtual Server 2005 R2 does not support the 64-bit guest systems required. For more information refer to “Exchange 2007 facing integration issues with other Microsoft software,” from Network World and further comment in Azaleos’ corporate blog.

For full details refer to, “Planning Processor and Memory Configurations,” “Best Practices for Deploying a New Exchange Organization,” and “Best Practices for Transitioning an Exchange Organization” from Microsoft TechNet.

1. Client Access Server.
   • Hardware. Microsoft recommends provisioning this server with 4 processor cores and 4GB RAM. Ensure at least a 100Mbps connection to the Mailbox Server. Enterprises with fewer than 3,000 mailboxes seeing average traffic or fewer than 1,000 mailboxes that see heavy traffic may consider using only 2 processor cores and 2 GB RAM. (In Microsoft parlance, “average” refers to an e-mail usage of 10 outbound/40 inbound messages a day. “Heavy” usage refers to 20 outbound/80 inbound messages a day. “Very heavy” usage describes workloads of 30 outbound/120 inbound messages a day.)
   • Network Architecture. Client Access Server is the first role that should be deployed and configured within the network topology. Each AD site that will also contain a Mailbox Server requires at least one Client Access Server. Proxies can be used to configure multiple Client Access Servers to present a single external address for OWA or ActiveSync access.

For detailed sizing information including Microsoft’s in-house experiences refer to, “Planning for Client Access Servers” and “Sizing Client Access Servers” from Microsoft TechNet.

1. Edge Transport Server.
   • Hardware. Microsoft recommends provisioning this server with 2 processor cores and 2GB of RAM. Monitor to determine if the volume and size of messages warrant adjustment.
   • Network Architecture. This role can be deployed at any time during the deployment. Also, Edge Transport Server can be deployed to an existing Exchange network without upgrading the other Exchange servers.

For full details refer to, “Planning for Edge Transport Servers,” “Planning for Edge Transport Features,” and “Planning for Address Rewriting” from Microsoft TechNet.

1. Hub Transport Server.
   • Hardware. Microsoft recommends 4 processor cores and 4GB of RAM. Using anti-virus/anti-spam on the Hub Transport Server may warrant an 8 core, 8GB RAM configuration.
   • Network Architecture. This role should be installed before the Mailbox Server or Unified Messaging Server roles, as those roles depend on the Hub Transport Server for mail delivery. Each AD site that also contains a Mailbox Server must contain at least one Hub Transport Server.

When contemplating e-mail flow in the Exchange infrastructure, be sure to review “Planning for Compliance,” “Overview of Compliance Features,” and “Planning for Domain Security” from Microsoft TechNet.

1. Mailbox Server.
   • Hardware. Microsoft recommends planning one processor core per 1000 average mailboxes. Double this for each higher level of usage. In other words, plan 2 processor cores for 1000 heavily used mailboxes; plan 4 processor cores for 1000 very heavily used mailboxes. Provision 3GB to 5GB of RAM per core (more for higher usage levels). Conversely, plan memory by allocating 2GB for every 4 Exchange Storage Groups on the server.
   • Network Architecture. The Mailbox Server role is strongly tied to Exchange storage choices and may be part of a Cluster Continuous Replication (CCR) or Local Continuous Replication (LCR) cluster (after Exchange 2007 SP1 launches, Standby Continuous Replication also becomes possible).

For additional information refer to, “Planning for Mailbox Servers,” “Planning Disk Storage,” “Planning for Local Continuous Replication,” and “Planning for Cluster Continuous Replication” from Microsoft TechNet.

1. Unified Messaging Server.
   • Hardware. Microsoft recommends 4 processor cores and 4GB of RAM. Converting WAV files to WMA files drives the hardware requirements for the Unified Messaging Server. Enterprises with minimal Unified Messaging Server activity may consider 2 cores with 2GB of RAM.
   • Network Architecture. Unified Messaging Server is the last server role to be installed into the Exchange network.

For full details refer to, “Planning for Unified Messaging Servers,” “Supported IP/VoIP Gateways,” and “IP/PBX and PBX Support” from Microsoft TechNet.

Bottom Line

Microsoft Exchange Server 2007 compartmentalizes e-messaging delivery workloads through a role-based architecture. Follow these recommendations to right-size server hardware for Exchange Server 2007 roles.

Tags: Exchange 2007, Right-sizing