vCenter “Hardware monitoring service on this host is not responding or not available” in Hardware Status tab

 

Fix: In vCenter, select the VM host, Configuration, Security Profile (under Software), Firewall Properties, CIM Server, Options, Restart.

After restarting the CIM Server service, it can take a few minutes before the hardware status is updated.

Tested in ESXi 5.0

Reference: http://communities.vmware.com/thread/219556?start=15&tstart=0

Watt and Volt-Amp (VA) Rating Notes

1. Definition and Purpose

• Watt is the real power drawn by the equipment.  The Watt rating to determine the actual power purchased from the utility company and the heat loading generated by the equipment.
• The VA rating is used for sizing wiring and circuit breakers.

2. IT Equipment Switching Power Supply Types

• Power Factor Corrected supply (PFC)
• Capacitor Input supply

3. Computer Equipment Watt and VA Rating

• Large computer equipment such as routers, switches, arrays, and servers made after 1996 use the PFC supply. Watt rating = VA rating
• PCs, small hubs, PC accessories, and larger computer equipment made prior to 1996 typically use Capacitor Input supply. Watt rating = 0.55 ~ 0.75 * VA rating

4. UPS Watt an VA Rating

• Small UPS: Watt rating = 60% * VA rating (a de-facto standard in the industry)
• Larger UPS: Watt rating = VA rating

5. Conclusion

• Neither the Watt nor the VA rating of a UPS may be exceeded
• Sizing the VA rating of a load to be no greater than 60% of the VA rating of the UPS ensures the Watt rating of a load not to exceed the Watt rating of the UPS.  This conservative sizing approach will typically oversize the UPS and provide additional run time.

Source: APC White Paper #15 “Watts and Volt-Amps: Powerful Confusion”