How is an Exchange 2013 Service Pack (SP) different from a Cumulative Update (CU)?

In a recent post to the EHLO blog, Microsoft reveled that Exchange 2013 SP1 will be released early next year. You can find that post here explaining some of the features that will be available.

One question that I have heard a few times from customers is “With Microsoft’s new update strategy, what is the difference between a Cumulative Update and a Service Pack?” The answer is not terribly straight forward, but I’ll attempt to make it as clear as possible.

With wave 15 of Exchange, and Lync as well, Microsoft has introduced a “Cumulative Update based process. This process is based around the idea that Microsoft will release Quarterly updates for Exchange. These updates will be full product builds, meaning you can install a complete Exchange server from each CU release, and will contain all previous security patches and product updates. So if you are building a new Exchange 2013 server today, you should do so using the CU3 files. There is no need to install Exchange 2013 RTM bits, then apply CU1, then CU2, then CU3.

With this new strategy, Microsoft is only supporting Exchange 2013 running the current CU and one CU back. That means if you were to call Microsoft and open an Exchange support case today, Microsoft may require to you update your Exchange 2013 servers to at least CU2 to resolve your issue.

On to the question at hand; how is a CU different from a SP in the Exchange 2013 world? As I said before, that is a pretty fuzzy line. According to Microsoft, a CU may contain security fixes, schema updates, and minor features while a SP may contain all that plus more significant features. The ehlo blog post announcing that SP1 is coming even says “thus SP1 is essentially CU4”.

Honestly, I think marketing is a major reason for the SP1 title of this release. Let’s face it, there are still plenty of people out there who hold to the old (and in my opinion outdated) thinking that you should not install a Microsoft product until SP1 is released. Calling this update SP1 is a signal to those people that it’s time to upgrade to Exchange 2013.