Why Hunting Zombie VMs Can Save Money

Posted by Mick McGuinness on 19 October 2017

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With Halloween only a couple of weeks away, we thought we would take a look at Zombie VMs and how you can eradicate them from your virtualised datacenter. Unlike the Zombies from TV and Movies, Zombie VMs do exist, but they don’t have to be scary. With the right tools and proper planning you can stop them taking over your datacenter.

What are Zombie VMs?

A Zombie VM is one which was provisioned but then never shut down once it was no longer needed. In a world where it is so easy to spin up a new virtual machine, it is easy to forget about them once you are finished using them. In pre-production there are many times when you need an environment just for a short period of time to do some testing but once it is complete, the VMs remain, consuming CPU, Memory, Disk and Power within your datacenter.

The cost of Zombie VMs

The percentage of VMs which can be classed as Zombie's varies greatly from organisation to organisation depending on what processes and governance are in place. If you assumed a relatively modest figure of 10% of your total VMs are Zombies, then a customer running 1000 VMs across 50 hosts could be wasting 5 full hosts. For a host costing around £10,000/year in power, licensing and other running costs so the total waste due to Zombies in this case would be £50k/year! And that is capacity which could be freed up to do something useful.

How to spot a Zombie

If you don't know what should be running in your environment, you have no way of knowing whether a VM should be there or not. Generally the bigger the environment, the more difficult this becomes. A single sysadmin can't possibly know the reason every VM exists. When the number of VMs may run to thousands this is a job for software and not a human operator. Spotting a Zombie typically needs to look at multiple measures to classify whether it is a Zombie candidate. Typically a Zombie would be a VM which uses very little CPU and Memory and has low network traffic in and out of it's interfaces.

Can tools can help?

Thankfully there are tools out there that can help you spot and kill zombies. The experts at AP have a history of helping customers with these kind of challenges and can help advise on the best strategy and tools to tackle Zombies in your environment.

Further reading

For more insight into the problem of Zombie VMs see this article from OpsDataStore.

Remember, if you don’t have a well-defined strategy for tracking VMs, your are at risk of a Zombie take over and that comes at a cost. 

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Tag: vmware, opsdatastore

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