We first noticed this problem when we moved all our VM's to datastores to an nSeries (NetApp box). VMware told us it is not an ESX issue, it is a storage system issue. So, we moved the VM's back to our DS8300. Now, we see the 'Lost access' errors occurring on the DS8300 storage. So, it does not seem to matter which storage system is hosting the datastores, the problem exists where ever we place the heaviest load. We have even seen these disconnects occur on the local storage.
I think we have had the 'Lost Access' issues all along we just didn't notice it until we migrated to the nSeries box. In our situation, I am convinced that these are ESX issues and/or configuration issues, not problems with the storage system. By ESX issues I mean things like timeout settings, queue depths, number of luns per port, and number of HBA's per port, etc.
