First published on TECHNET on Apr 08, 2011
I am Greg Cusanza, Program Manager on the SCVMM team. Today I am going to blog about one of the interesting new features of VMM 2012, which is the ability to control the power state of a host.
We use both in-band methods that work through the host’s operating system and out-of-band (OOB) methods that use hardware base-board management controllers (BMCs) on servers to be able to discover the servers, query the power state, power them on, power them off, and reboot.
In-Band vs. Out-of-band
In-band is used for a clean shut downs or reboots when there is an operating system on the host that we can communicate with. Through the UI VMM only turns off a host using in-band methods because a clean shut down is always best. VMM supports in-band for all host operating systems that it can manage. Of course VMM will only turn a host off if there is a way to turn the host back on. If shut down is disabled in the UI this is likely why. That’s where out-of-band comes into play and a BMC is required. The out-of-band channel is able to control the power state regardless of whether the host is on, off or if there is even an operating system installed.
Power management Enables OS Deployment and Power Optimization
While power control is interesting on its own, the real power is in the features it enables.
OS Deployment requires out of band discovery to find computers that exist on the network, even if they are new and don’t have an OS yet. We use the out of band channel to reboot the new hosts into a PXE environment where we are able to deploy a fresh Microsoft Window Server OS with Hyper-V.
We also have Power Optimization (PO) for clusters. PO lets VMM turn off cluster nodes that are not needed during off-peak times, and more importantly lets VMM turn them back on when they are eventually needed.
In order to communicate with a BMC VMM has to talk to the BMC in a protocol that it can understand. In the box we support two standards based protocols:
* Intelligent Platform Management Interface (IPMI) / Data Center Management Interface (DCMI)
* Systems Management Architecture for Server Hardware (SMASH) over WS-MAN
You may be more familiar with brand specific names for your hardware, such as Dell DRAC or Hewlett Packard iLO. You may not know what protocols they support. Chances are regardless of the vendor these products generally understand one of the above protocols. You can find out what is supported from your product’s documentation. If you can’t find the product’s documentation then IPMI/DCMI is a good choice since most BMC hardware supports it. You may need to enable the protocol in the BMC’s firmware since it isn’t always enabled by default or you may need to upgrade the firmware to a newer version. This is the case with HP iLO2.
If you have a type of hardware that does not support either of the above protocols you still have an option. We made our OOB power feature extensible by supporting external configuration providers. These are in the form of PowerShell modules that you can write to implement the discovery, power on, power off, power reset, etc. for other non-standard hardware types. They can be written as PowerShell scripts, or using a .NET language. As long as you have some hat’s topic I’ll save for later.