Over the last several months, I have been involved in several critical customer escalations (what we refer to as critsits) for Exchange 2010 and Exchange 2013. As a result of my involvement, I ha...
Updated Apr 27, 2020
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Labs can be very cost prohibitive especially if you run an Exchange hosting business based on private cloud and resource forest model. Also, labs don't always allow you to simulate traffic and load.
While upgrading a 2007 customer to 2013 we hit an issue where the 2013 servers would send almost all of the traffic to one 2007 CAS for the un-migrated mailboxes. The legacy CAS became overloaded and started refusing connections leading to a mass outage. After
a 20 hour critsit with MS support we were told there was an "undocumented fix" that was included in 2013 SP1 which had been released 2 weeks prior.
After installing CU6 for 2013 in November we hit a problem where mailboxes databases failed over multiple times during the day. We had to install an Interim Update to fix it (http://support.microsoft.com/kb/2997209).
The Interim Update caused problems with the OWA UI when users would select Options. We now have to uninstall the interim update before CU7 can be applied.
Both these problems could have been avoided if Microsoft had tested the 2013 CU more thoroughly before releasing. It appears that because you don't have any co-existence in O365 you don't test it so on-premise customers are left to test in the field.
There is fine balance between being on the latest and greatest release and a tried and trusted release!
Have to admit I'm apprehensive about installing CU7 for 2013, but I have a group of Russian users who are becoming more vocal about their DST update.
Mitchell.