Be careful when updating you ESXi hosts from VMware vSphere 5.0 to 5.1. The following servers were supported in 5.0 but are no longer supported in 5.1:
- HP ProLiant BL260c G5 - No vSphere ESXi 5.1 Support
- HP ProLiant BL460C - No vSphere ESXi 5.1 Support
- HP ProLiant BL460c G5 - No vSphere ESXi 5.1 Support
- HP ProLiant BL465c G5 - No vSphere ESXi 5.1 Support
- HP ProLiant BL480C - No vSphere ESXi 5.1 Support
- HP ProLiant BL495c G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL360 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL365 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL380 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL385 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL385 G5p - No vSphere ESXi 5.1 Support
- HP ProLiant DL585 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant DL785 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant ML350 G5 - No vSphere ESXi 5.1 Support
- HP ProLiant ML370 G5 - No vSphere ESXi 5.1 Support
- IBM System x3850 M2 - No vSphere ESXi 5.1 Support
- IBM System x3950 M2 - No vSphere ESXi 5.1 Support
- IBM System x3950 M2 2 Node - No vSphere ESXi 5.1 Support
- IBM System x3950 M2 4 Node - No vSphere ESXi 5.1 Support
- Winchester Systems Inc FlashServer HA-4100 - No vSphere ESXi 5.1 Support
- Cisco UCS - C200 M1 Rack Server - No vSphere ESXi 5.1 Support
- Cisco UCS - C210 M1 Rack Server - No vSphere ESXi 5.1 Support
- Cisco UCS - C250 M1 Rack Server - No vSphere ESXi 5.1 Support
Source: VMware HCL