Windows Update is now offering the the .NET Framework 4.5.2 update as an "Important" update to Windows computers.
- Microsoft .NET Framework 4.5.2 for Windows 8.1 and Windows Server 2012 R2 for x64-based Systems (KB2934520)
- Microsoft .NET Framework 4.5.2 for Windows Server 2008 R2 for x64-based Systems (KB2901983)
Both of these updates require a restart. .NET 4.5.2 is not required for current versions of Exchange server, but if your servers or patching process uses Windows Update you will see these updates are being pushed to them anyway.
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Windows Update on Windows Server 2012 R2 |
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Windows Update on Windows Server 2008 R2 |
Be aware that when this update is installed on your Windows servers it will re-optimize all .NET assemblies on the server when it restarts. Perfmon shows ~99% of CPU resources are in use for about 8-10 minutes while this occurs
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98% CPU Utilization After Restart |
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.NET Runtime Optimization Service Racing |
The main culprit is the mscorsvw.exe process (The .NET Runtime Optimization Service), as shown above. Exchange uses .NET assemblies extensively in its own code, so this optimization will affect the server's ability to function properly until this process completes. Because of this, it will take significantly longer for the server to restart and system performance will be very very poor.
Once the the re-optimization process completes the Exchange server performance will eventually return to normal. This may take some time because other processes such as the IIS Worker processes and Exchange services were starved for resources. In some cases I have seen Exchange services, such as the Microsoft Exchange Transport service, fail to start. Make sure all your services are running before moving on to patch the next server. I even suggest restarting the patched server just to make sure it restarts normally and all services start properly first.
from Exchange News
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