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Zombie Servers – Hunting Down The Lost Capital

April 3, 2023 | Insights,

The problem of servers that use electricity but deliver no useful information services, (known as zombie or comatose servers) is one that continues to haunt the data centre industry. Few companies can identify these orphaned servers, and many companies don’t even know how many servers they have.

In 2015, Jon Taylor of Anthesis Group in partnership with Jonathan Koomey Research Fellow at Stanford University, published leading research revealing that 30% of enterprise servers in the five facility, 4000 server sample were comatose, performing no useful computing over a 6 month period or more.

The original research highlighted that more than $30 billion of data centre capital was sitting idle. Not surprisingly this research received widespread news coverage, including headlines such as “Millions of ghost data centre servers hold $30bn profit” (CBR, June 2015) “Pull the plug on comatose servers to save money and the planet” (Tech Republic, June 2015). The findings implied that there were about 10 million zombie or comatose servers worldwide-including standalone servers and host servers in virtual environments.

The findings supported previous research performed by the Uptime Institute, which also found that around 30 % of servers were unused, with the 10 million estimated zombie servers translating into at least $30 billion in data centre capital sitting idle globally (assuming an average server cost of $3,000 while ignoring infrastructure capital costs as well as operating costs).

Two years later, the dataset from which the original findings were drawn grew from 4,000 physical servers to more than 16,000 physical servers and additional information on 32,000 virtual machines (VM) running on hypervisors. The new findings showed improvements, as well as an alarming wake-up call.


Virtualisation without improved measurement technologies and altered institutional practices is not a panacea. Without visibility into the scale of these wasted resources, the problem will continue to challenge the data centre industry.

On the upside: when an enterprise acted to remove physical zombie servers when presented with evidence of the problem’s magnitude, they were able to reduce the amount from 30 percent to eight percent in just one year. On the downside: new data showed that some 30 percent of VMs are zombies, demonstrating that the same discovery, measurement, and management challenges that apply to physical servers also apply to VMs.

The study confirmed that the issue is not being adequately addressed. New data indicates that one-quarter to one-third of data centre investments are tied up with zombie servers, both physical and virtual. While few companies can identify them, zombie servers pose a costly problem for data centres. The ability to eliminate them can result in considerable capital and operational savings when one takes into account resources needlessly wasted on power, hardware, licenses maintenance, staffing and floor space.

Finding and eliminating comatose servers would also save many enterprises money, but more importantly, taking that action would eliminate an unappreciated security risk. Zombie servers are unlikely to have the latest security patches, which makes them an open door to many enterprise data centres. If the monetary incentives are not enough to ensure prompt action, concern over cybersecurity should.

Findings from the second report

In this follow-up analysis, we assessed the percentage of comatose servers in a sample four times larger than included in our original report (and covering twice as many facilities) using a consistent methodology and data from TSO Logic’s data discovery tools. This report summarises these new results, which includes an assessment of comatose physical servers as well as comatose virtual machines running on hypervisors.

Download the zombie servers report

To find out more information on how Anthesis can help your business can address the challenges and opportunities of Zombie servers in your own business please contact Jon Taylor, or alternatively, fill out the form below:

“In the twenty-first century, every company is an IT company, yet far too little attention is given to IT inefficiencies, and to the need for widespread changes in how IT resources are built, provisioned and managed.”

Dr. Koomey

“Far too many businesses have massive IT infrastructure inefficiencies of which they are not even aware,” said Jon Taylor, partner at Anthesis. “These preliminary findings support the idea that ongoing measurement and management of a business’s IT infrastructure is needed to optimise performance, energy use and return-on-investment,” he added.

Dr. Koomey said: “Removing idle servers would result in gigawatt-scale reductions in global IT load, the displaced power use from which could then support new IT loads that actually deliver business value. That’s a result that everyone should cheer.”

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