Anytime you make changes to the SAN as far as adding or removing LUNs and things like that. Do a rescan for datastores on your hosts. If you dont it will cause issues. My VMs would blank out every view minutes when I forgot to rescan. Hope this helps.
I've run into this issue with HDS, and a cold boot was the only way to get things back in order. See this kb for a description of what may have happened.
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