Power Management for Hyper-V (Part 2)

by [Published on 7 April 2010 / Last Updated on 7 April 2010]

Some reasons why larger organizations need to adopt different tactics when considering power management techniques discussed in the previous article.

If you would like to read the first part of this article series please go to Power Management for Hyper-V (Part 1).

Introduction

In the first part of this article series, I explained the steps that I have taken to protect my virtualization hosts and the virtual machines residing on them against power failures. Although the technique that I am using seems to work really well for me, it is important to keep in mind that my network is far simpler than what most medium and large sized businesses use. As such, I realize that what works for me may not be practical for some organizations. That being the case, I want to conclude the series by discussing some other options for preventing power failures on servers running Hyper-V.

External Devices

One of the things that differentiates my virtualization host servers from those used in many other organizations is that my servers are completely self contained. For example, the server shown in the screen captures in Part 1 contains an integrated six disk array in addition to the disk containing the system volume.

The reason why this is significant is because the server’s storage array is powered by the server’s own internal power supply. In contrast, many organizations who use direct attached storage do so in the form of external storage arrays with their own dedicated power supplies. Larger organizations often use shared storage (which is useful for vMotion or Live Migration) or even host virtual hard drives on a SAN.

My point is that using external storage arrays complicates power management. After all, being able to gracefully shut down your virtual machines means nothing if your storage arrays run out of power before the shut down process is complete.

Using external storage is not always problematic. There are plenty of storage vendors who offer storage arrays with built-in battery backups. The trick is to be able to accurately determine how long a storage array can run on battery power. Once you know how long your storage array can run on battery power, you can configure your virtualization hosts to shut down before the storage array can run out of power.

If you have a large enough UPS, you may be able to get away with plugging your storage array into the same UPS as your virtualization host servers. Although doing so will decrease the amount of time that your batteries will keep the server online, it does help to ensure that the storage array does not run out of power before the server does.

Hyper-V Aware Power Management Software

Another reason why my virtualization hosts may not accurately reflect what some other organizations are using is because I am running Hyper-V on top of Windows Server 2008 R2 Enterprise Edition. As you may recall, I am running APC PowerChute on my host servers. This would not have been possible if I were running Hyper-V on a server core deployment or if I ran the standalone version of Hyper-V Server.

It always seems that there is a tradeoff between flexibility and performance. Running Windows Server 2008 with a GUI gives me lots of flexibility and allows me to use low end power management software, but it diminishes the server’s performance because the GUI consumes some CPU cycles and other server resources that could have been used by the virtual machines. Even if server performance weren’t an issue, many organizations prefer to use non GUI based Hyper-V deployments because doing so is an effective way of reducing the host server’s attack surface.

At any rate, if your virtualization host servers are not running a GUI, then it means that you won’t be able to perform power management in the way that I described in the previous article. Thankfully, there are still some viable power management options available.

One of the best solutions that I have found is to use an application made by APC called PowerChute Network Shutdown for Hyper-V. As the name implies, PowerChute Network Shutdown for Hyper-V is a special version of PowerChute that is especially designed for use with host servers that are running Hyper-V.

Before I begin talking about everything that the software does, I should point out that PowerChute Network Shutdown for Hyper-V is not compatible with all APC UPSs. Presently, the software works with the following APC models: any Smart-UPS with a card slot or an embedded Network Management Card, any Smart-UPS DP UPS, any Symmetra UPS, or any Silicon Series UPS.

The reason why only specific UPS models are supported is because the software requires each UPS to have an APC Network Management Card installed. Additionally, the network card must be running firmware version 3.3.1 or later.

So what makes PowerChute Network Shutdown for Hyper-V different from any other edition of the PowerChute software? Well, because the application is specifically designed for virtualization hosts, it coordinates and confirms the shutdown of virtual servers prior to the UPS running out of battery power. The solution that I presented in the previous article generally works, but there is no way for the power management software to be able to confirm that all of the virtual machines have shut down before the battery runs out of power. All you can do is to try to begin the shut down sequence early enough to allow it to complete before the batteries run out of power.

Another major difference between PowerChute Network Shutdown for Hyper-V and some of the other editions of PowerChute is that the software is not dependent on the server running a GUI based operating system. Instead, the UPS is configured to act as a Web server. The network administrator is therefore able to manage the UPS by establishing an HTTPS session with it, and using a Web browser to interact with the UPS’s management interface.

Because the UPS is network enabled, there is no USB cable connecting the UPS to the server. Instead, the UPS communicates with network servers using a designated network port. This approach makes it possible for a single UPS to manage multiple virtualization host servers. If you need to use a USB connection to your UPS for some reason, then you will have to use PowerChute Business Edition. Keep in mind though that versions of PowerChute Business Edition above 8.0 cannot be used on Windows Server 2008 machines that have the Hyper-V role installed. It is also worth noting that PowerChute Business Edition does not come with any special mechanisms for shutting down virtual machines.

Even PowerChute Network Shutdown for Hyper-V cannot automatically shut down all virtual machines. The software only works for virtual machines on which the integration services have been installed and the Automatic Stop Action has been set to “Shut Down the Guest Operating System”.

Conclusion

As you can see, managing battery power for virtualization hosts can be tricky. Smaller organizations may be able to get away with using a power management solution such as the one that I discussed in the previous article, but larger organizations will typically require specialized hardware and software.

If you want to learn more about PowerChute Network Shutdown for Hyper-V, you can read the product overview here. At the time that this article was written (November of 2009), a license for a single physical server was listed at $99.99. APC also offers a similar application that is designed for VMware.

If you would like to be notified of when Brien Posey releases the next part in this article series please sign up to our VirtualizationAdmin.com Real Time Article Update newsletter.

If you would like to read the first part of this article series please go to Power Management for Hyper-V (Part 1).

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