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Installing VMware vSphere Storage Appliance 5.1 in a vSphere 5.0 environment (2041373)
The VMware Product Interoperability Matrix indicates that you can install VSA 5.1 in an environment with vCenter Server 5.0 and ESXi 5.0.
However, when vCenter Server is upgraded to 5.1, the extension information for VSA is lost and the plug-in does not load. This does not affect data or virtual machines running on the cluster.
After upgrading to vCenter Server 5.1, you must uninstall and reinstall the VSA Manager.
Note: If you tried other troubleshooting steps before uninstalling and reinstalling the VSA Manager, there may be other issues that need to be addressed. If you experience any unexpected behavior, file a Support Request. For more information, see Filing a Support Request in My VMware (2006985).
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