couple of weeks ago something very strange was affecting one virtual machine. our monitoring solution showed the VM losing connectivity every couple of minutes. the windows system logs showed “LSI_SCSI Event 129 – Reset to device, \Device\RaidPort2, was issued”  occurring every minute. clearly sounded like a storage issue, but the SAN performance was fine at the time. we tried uninstalling and reinstalling vmware tools with no luck.

eventually, we noticed the vm hardware version was still 4, as this particular vm had been around since ESX 3.x. so we did a vm hardware upgrade to version 7 and the issue (so far) has disappeared.