Exchange Server 2010 and Service Level Agreements

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E-mail is an essential tool for collaboration and knowledge sharing in modern organizations, in addition to being a tool for doing external business. High availability of the e-mail service helps maintain high levels of employee productivity and creativity in these organizations. It is in this context that a service level agreement (SLA) to make e-mail servers available at levels like 99.99 percent of the time becomes significant.

An SLA of that level means just one hour of downtime per mailbox per year. The service provider commits to making e-mail available at this level under such an SLA. We look at how Exchange Server. 2010, among other SLAs, makes this possible.

By making all server downtimes (planned and unplanned, resulting from a problem in the Exchange, network or hardware, or even from a natural disaster) count against the SLA, the service provider is not allowed any excuse for unavailability of e-mails.

Such a high performance becomes possible only if there are regular reviews of what is happening on the ground, and how any deviations from agreed levels came about. Setting targets is easy; even measuring what happened is comparatively easy; it is analyzing the real reasons for the happenings that can become a complex exercise. It is this analysis and resultant identification of causes that makes effective remedial action possible.

The quality of e-mail service is measured in terms of:

  • Continued server availability
  • Timely delivery of the mails
  • Availability of e-mail clients

How Exchange Server is Equipped for the Task

Exchange 2010 has unified messaging such as voice telephony and instant messaging as well as e-mail, and server downtimes can affect these other services also. Several new features and improvements in Exchange Server 2010 helps achieve the goal of high availability:

  • The newly introduced Data Availability Groups (DAG) include up to 16 mailbox servers that host the messaging databases. Each server’s database is copied to other servers so that in case of problems with the original, traffic can be switched over to the copy and continued availability of the messaging functionality can be ensured.
  • DAG also allows continued availability of e-mail (and other messaging services) even during maintenance shutdowns of particular servers as the mailbox copies maintained on other servers (up to 16) become available to users. Unplanned shutdowns owing to server problems are tackled through automated switchovers
  • Built-in performance measurement tools such as LoadGen allows relevant factors to be measured so that system planners can configure processor and memory capacities (for example) to cope with the expected requirements. Configuration of Exchange Server 2010 for optimum performance is discussed at
  • Specialization of server roles in 2010, such as Client Access to Mailbox, makes it more reliable, flexible, and scalable, in turn leading to higher availability of services.

A whitepaper at discusses the Exchange Server 2010 operating environment in specific detail.

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