As most of you probably know, last week was TechEd North America. The sessions on Exchange 2013 did disclose some changes for Cumulative Update 2 (CU2), which – according to the announced CU cadence – should arrive somewhere in the summer, most likely July. For those who didn’t follow my Live Tweeting from the event, here’s a quick summary of the announced or probable changes for CU2.

The return of 100 DB Limit
Exchange 2013 CU2 Enterprise Edition will bump the limit for the number of database per server from 50 to 100. The initial limit to 50 for Exchange 2013 RTM (and CU1) is said to be chosen due to performance reasons, but many customers complained they want to host more databases per server. For CU2, Microsoft made changes which enable increasing this limit to 100 again. Perhaps the customers complaining transitioned from or are currently running Exchange 2010, and are facing having to introduce additional servers to host an equal number of databases. In such cases, be advised that regardless of this increased limit, Exchange 2010 and 2013 are not directly comparable and you should utilize the Exchange 2013 Server Role Requirements Calculator to size your Exchange 2013 environment (an update will follow as soon as CU2 becomes available). An important side note to keep in mind with all this is that adding (or removing) databases in Exchange 2013 requires a restart of the Information Store service, so you might prefer maximizing the number of databases from the start, not when required to, so you’ll avoid having to shut down services or having to move mailboxes around to comply with your SLAs.

Single Sign-On Redirects
Exchange 2013 CU2 will introduce Single Sign-On (SSO) by enabling silent redirects for Outlook Web App (OWA) to downlevel CAS servers when the mailbox is hosted on a downlevel mailbox server when they’re configured with a different ExternalURL (e.g. in a different internet-facing site).

DAG Management Service
The to be introduced MSExchangeDAGMgmt service will offload the Replication service by hosting the Replication Service MonitoringComponent, providing information on health status, logging events in the same location MSExchangeRepl used to, i.e. Application Eventlog using the same Crimson channel, but still using MSExchangeRepl as source.

DAG Witness Server in Azure (possibly!)
When you’re an Azure subscriber, a feature possibly included in CU2 will allow your DAG Witness Server to be located in Azure. This allows for example customers with 2 physical datacenters to utilize automatic site fail-over, as automatic site fail-over normally requires a 3rd well connected datacenter for hosting the Witness Server. From an Azure perspective, the Witness Server will be single File Server on Azure IaaS VM or two File Servers using persistent VMs with XStore shared storage. Note that extending Active Directory permissions to the Public Cloud is required for this option.

Responder Throttling per Group
Responders are part of Exchange 2013’s Managed Availability, and define if and how to act on generated alerts, e.g. restart a service or take a Mailbox server out of service. In CU2, several responders will be throttled per group, e.g. DAG, instead of per server.

ARR Support
Not CU2 related, but it was announced that support for ARR, which stands for IIS Application Request Routing, is coming for Exchange 2013. With the discontinuation of TMG, customers are looking for alternatives to publish their Exchange 2013 (or Lync web services) and ARR is one of them, often used because it utilizes IIS and is free despite it lacking some of TMG’s features. A clue for this could lie in one of the features announced for Windows Server 2012 R2, which will contain a Web Application Proxy, which basically will be an HTTP reverse proxy aimed at publishing corporate resources for access from the public network.