Earlier this week we started the process to upgrade one of our hypervisor compute clusters when we encountered a rather painful bug with HP’s Broadcom NIC chipsets. We were part way through a routine rolling pool upgrade of our hypervisor (XenServer) cluster when we observed unexpected and intermittent loss of connectivity between several VMs, then entire XenServer hosts. The problems appeared to impact hosts that hadn’t yet upgraded to XenServer 7.2. We now attribute this to a symptom of...