Virtual sprawl is caused by uncontrolled deployment of Virtual Machines (VMs). Server virtualization has the potential to lower overall IT costs by improving efficiency of server usage. This is only realized if the virtual machines continue to be used productively. If VMs continue to run after they’re no longer required, the initial savings gained from virtualization will be lost with increased costs from power, cooling, licensing and management. NightWatchman Server Edition identifies virtual machines which are not being used so you can reclaim resources for new VMs.
Virtual server sprawl may replace physical server sprawl, resulting in server hardware (and operations) inefficiencies. (Gartner 2009)
The costs associated with virtual machine sprawl:
Facilities
The power required to run a virtual host can be significantly more than an x86 server due to the number of CPUs, amount of disk storage and increased heat output requiring additional cooling. If VM sprawl is not managed, energy demand will increase considerably.
Server Hardware
There is a risk that VM sprawl will replace physical server sprawl. Neglecting to manage the deployment of virtual machines could result in hardware and operations inefficiencies.
Storage Hardware
As the number of VMs increase as does the required storage, resulting in a possible increase in storage hardware. Backing up these additional images takes time, and this can sometimes be difficult to achieve in the given maintenance window.
Software Licenses
It cannot be assumed that a license from a physical server can be converted to a VM license without additional costs. Some software vendors require a license for each server on the virtual host. VM sprawl can lead to spiraling costs for purchasing additional licenses.
Operation & Administration
Each VM requires management in the form of monitoring, patching and security. Each additional VM deployed adds to this burden.
Source:
Forrester (2009) Storage Choices For Virtual Server Environments. Andrew Reichman with Stephanie Balaouras and Christian Kane
Gartner (2009) Dataquest Insight: Server Virtualization and IT Operations Management Will Boost End-to-End Green Branding and Positioning in EMEA. Rene Millman, Mike Spink
Gartner (2009) Server Virtualization for x86: A Benefits Impact Assessment. Cameron Haight, Stewart Buchanan, Thomas J. Bittman