I had encountered an error during the VSphere environment upgrade to version 6.0. All components upgrade went smooth except the error I encountered after the ESXi host upgrade.
The host started reporting as "Deprecated VMFS volume(s) found on the host. Please consider upgrading volume(s) to the latest version".
I was not sure about why is this alert because I already upgraded my VMFS volumes to the latest version post Host upgrade & the ESXi host hostd.log was also pointing to the same error.
I had restarted the ESXi host & after the reboot the alert was gone.
While browsing VMware KB's I came to know that this is a known issue & tagged as false positive & restarting of management agents itself will fix this it seems.
Cause for the issue has been detailed in the KB article KB2109735(http://kb.vmware.com/kb/2109735).