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Managing Powered-Off Virtual Machines

I recently took a look at one of the larger VMware vSphere and Microsoft Hyper-V environments I work with, and noticed that I had high number of powered-off VMs. Approximately 35 percent of the environment's nearly 800 VMs were powered off. This is a practice of mine in my home labs, but I was shocked to see how somewhat sloppy I've become with powered-off VMs outside of that setting.

Given that this is a large number of powered off VMs, a few interesting attributes come into play. First of all, I was holding on to these VMs "only if I'd need them"; and based on the timestamps of the its last activity, it was usually quite awhile ago. Secondly, I really don't have the infrastructure size to power them all on at once. These two characteristics made me wonder if I really need to hold on to them any more.

Backup, Then Delete
I've decided it's best to back these VMs up and then delete them. I like the idea of backing them up, as almost any backup technology will have some form of compression and deduplication, which will save some space. And by holding on to these unused VMs, I've been effectively provisioning precious VMware vSphere and Microsoft Hyper-V primary datastore and volume space for something I may not use again. Reclaiming that primary space is a good idea.

This is especially the case since I'm going to start getting back into Windows Server Technical Preview and the Hyper-V features soon. At Microsoft Ignite I took a serious look at the Hyper-V and next-generation Windows features, as I'm very interested in both them and the bigger picture, especially as it works with Microsoft Azure.

Another consideration is the size of the environment. In the larger, non-lab setting, I find it makes more sense to back up the VMs, then delete them. For smaller environments, it may make more sense to leave the VMs on the disk rather than deleting them all.

Tips and Tricks
Speaking of powered-off VMs for lab use, I did pick up an additional trick worth sharing. There are plenty of situations where a powered-on VM makes more sense than one that's powered off. For those, there are several ways to have powered-on VMs that are more accessible, but take up fewer resources:

  • Set up Windows Deployment Services and PXE boot VMs with no hard drive. They'll go right to the start of the Windows installer menu (but without a hard drive, they won't install) and have a console to see, but they don't do much.
  • Leverage a very small Linux distribution. DSL, for example, is only around 50 MB. (More options for this have been blogged about by my good friend Vladan Seget.)
How do you handle the powered-off VM? Do you archive them via a backup and then delete them or put them on a special datastore or volume, and use them when you need them? There's no clear best practice for both lab and non-lab environments, but I'm curious if any of you have tips to share.

Posted by Rick Vanover on 05/12/2015 at 8:21 AM


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