How will Cumulative Updates work under the new Servicing Model for Exchange 2013

On April 2nd 2013, Microsoft released cumulative update 1 for Exchange 2013. This is the first release using the new servicing model for Exchange Server 2013 (see The Exchange Team Blog for more information).

Below are some of the most commonly asked questions regarding the introduction of a Cumulative update.


Q: Will CU’s contain product fixes only or will new features be included as well?

A: CU’s will be used to deliver fixes for on-premises and online customer reported issues as well as items identified by the Exchange team. Feature changes due to customer requested design changes may also be included which could add or modify existing functionality.

Q: Will there continue to be Service Pack releases?

A: Similar to previous releases, it is anticipated that periodic Service Pack updates may be provided.

Q: Will AD schema changes be included in CU’s?

A: AD schema updates may be included in a CU if required to support a change in functionality. AD Schema updates for Exchange are additive and always backwards compatible with previous releases and versions.

Q: Will there be multiple security updates released for a given CU?

A: The security updates released will be CU specific and will contain all of the fixes available at the time of release for a given CU in a single cumulative package. In the event that multiple releases have been made available for a given CU, only the most recent version of the security update package will be required to be installed and it will contain all previous fixes as well.

Q: If I am installing the most recent CU available, will I need to apply security updates to that release.

A: Not necessarily. When we release a CU it will contain all security updates currently available. Only if a security update is made available after the release of the CU, will it be necessary to apply an additional security update on top of a CU. Security updates will clearly indicate which CU they are intended to be used with.

Q: Will the server version be updated during the install of a CU?

A: Yes, this also addresses some customer feedback.

Q: How long is a CU supported?

A: A CU will be supported for a period of three (3) months after the release date of the next CU. For example, if CU1 is released on 3/1 and CU2 is released on 6/1, CU1 support will end on 9/1.

Q: How do I recover from a failed installation of a CU?

A: Exchange Server 2013 includes high availability options to prevent the loss of data or functionality due to the upgrade of a single server. Furthermore, Exchange Setup is engineered to be executed, repeatedly if necessary, until a server installation or upgrade is completed. The actual steps used to recover from a failed CU upgrade will vary based upon the point at which the failure occurs and customer configuration. Existing mechanisms used to recover from a failed service pack installation will be applicable and may include use of SETUP /m:RecoverServer or installing a new server object and reseeding or reattaching existing DB’s.

Q: How will CU’s be made available?

A: CU’s will be published on the Microsoft Download Center. Security updates for a CU will be made available on Microsoft Update and the Microsoft Download Center.

Q: In a Database Availability Group configuration do all servers need to be at the same CU revision?

A: Customers should plan their deployments such that all servers in a Database Availability Group are running the same CU revision for the version of the product they are using. During a CU upgrade, it is supported for individual servers in the Database Availability Group to be deployed with different CU versions. This is expected to be a temporary condition until all servers have been upgraded.

Q: Do all servers in a Client Access Array need to be at the same CU revision?

A: Similar to Database Availability Groups, co-existence of multiple CU revisions in a single array is supported during the upgrade process.

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