As your organization grows, so do mailboxes and, with them, storage requirements. You will therefore need to make some scalability tweaks and design considerations in accordance with this growth. In this post I shall outline the best Exchange Server 2010 scalability methods any Exchange admin should consider.

Server Roles

Thankfully, Exchange Server 2010 makes it intuitive to scale Exchange deployments with its various clearly defined server roles. A small business can probably install the different server roles (Except Edge Transport Server) onto a physical server, and expand by deploying heavily loaded roles into the new physical server in tandem with the growth of the company.

  • Client Access Server (CAS) – Hosts client access via protocols such as POP3, IMAP4, ActiveSync, Outlook Web Access and Outlook Anywhere.
  • Edge Transport Server – Typically deployed at the network perimeter or DMZ, this facilitates content filtering before forwarding them onto the Hub Transport Server.
  • Hub Transport Server – Works as an internal mail delivery system.
  • Mailbox Server – Acts as a backend store house to host mailboxes and public folders.
  • Unified Messaging Server – Links up a Private Branch PBX system to Exchange 2010 for voice messaging and fax capabilities.

Clearly, an understanding of the various Server Roles and how they can be expanded is crucial to being able to scale Exchange Server 2010 to support a larger number of clients.

Third-Party Applications

An important but often overlooked consideration is the presence of third-party monitoring applications. For example, internal network appliances may need to relay mail off Exchange Server’s SMTP engine to send out important email alerts to administrators, and CRM (Customer Relationship Management) portals or other internal applications may also generate a hefty load on this front.

Apart from relaying email messages through the SMTP engine, Microsoft has designed Exchange to support hooks for third-party software such as antimalware scanners, backup software, fax software and other phone/PBX features. As this will also have an impact on the system performance, knowing from beforehand how these third-party applications interact with Exchange pays off.

Database Availability Groups

Database Availability Groups (DAGs), is a feature in Exchange 2010 that allows for multiple databases to be spread across multiple servers. While the use of DAGs is primarily geared towards high availability and site resilience, its strengths do address the primary pain points when scaling an Exchange deployment.

Specifically, because DAG allows for multiple databases that tend to be smaller in size, restoration of an individual database from offline storage can complete in a smaller time window compared to a larger database. In addition, risk is mitigated by distributing mailboxes across multiple databases; failure of a single database will only inconvenience users contained within that specific database, instead of all users in an organization.

Configure Your Disk for Performance

A common problem that can severely reduce the efficiency and speed of your Exchange Server would be poor disk performance as server workload increases. One easy way of mitigating this, so that an existing deployment can be scaled without having to rebuild it, would be to separate the Exchange Server database and log files into separate hard drive volumes.

Because log files predominantly consist of write operations, in the same way that the majority of mailbox database accesses are read operations, a relatively clean separation can be achieved by simply storing Exchange and server log files in a separate physically volume from the Exchange databases.

Obviously, other methods exist with which to boost disk performance. Switching to Solid State Drive (SSD) will bring about a tremendous improvement in read and write speeds, but at a much higher per megabyte cost.

There are many considerations that play a part in stretching the scalability of an Exchange Server deployment, and we hope that the above tips will help you plan better, as well as to squeeze some more life out of existing deployments.


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