Server Virtualization: 6 Management Myths

Hint: You don't really know what hypervisors you're running, or what it all costs. Consider some expert advice on 6 common management mistakes.

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5. Managing performance will require a wide range of IT skills.

Perhaps the biggest problem in virtualized deployments is that sometimes, even the IT people responsible for them don't really understand how to set up the infrastructure so it's easier to manage, or manage capacity to the detailed level required, according to Patrick Kuo, a Washington, D.C.-area consultant. Kuo has helped build web and virtual-server infrastructures at Dow Jones, the U.S. Supreme Court, the Defense Information Services Agency and, most recently, D.C. political-news site The Daily Caller.

When physical servers or server farms run into performance problems, IT managers can run in a higher-bandwidth Internet connection or add servers — an approach that limits itself because of the cost and logistical difficulty of adding new physical resources, he says.

Virtualized infrastructures don't have those limits, so the IT people designing the virtual infrastructure have to divide data-center resources in ways they may not have done before, if their backgrounds are limited to systems management rather than including networking, applications management or other disciplines.

"With Daily Caller, and with some other clients we've been able to get better performance with a four-tier architecture that puts a layer of caching first, and the app servers, the web servers behind that, and a replicated database backing them up. The fourth tier is a non-production layer for the editors or content contributors to work with," Kuo says.

N-tier architecture is a basic part of data-center and enterprise-application design, but is often not part of the background, responsibility or expectations of IT managers responsible for virtualization.

Looking at server or application performance as standalone metrics, rather than as an indication of how the whole data-center IT stack functions, puts too much emphasis on the performance of the hardware, rather than managing resources carefully to get the best performance out of the hardware available.

"People tend not to think of tuning in virtualization, but especially in enterprise apps you have to get down into the details. You have to see how the instances are performing under specific workloads and look at the trends and do some analysis on what would happen if your utilization jumped from 80 percent to 90 percent and add resources to the layer that needs it," Kuo says.

6. Cost isn't the only thing that comes with a virtual multiplier.

Not every virtual server is the same, but everything you do to one virtual machine, you generally have to do to all the others, according to Phil Hochmuth, program manager for security products at IDC.

The normal way to monitor physical servers is to install a lightweight software agent that will collect and report performance data to the main console, he says.

With virtual servers, that means installing one agent on the physical server and one each on each VM, he says.

IDC's December report on server virtualization predicts an average of 8.5 VMs per server by 2014. That means not one agent running on each physical server, but 9 or 10, each of which uses additional resources, each of which requires an additional license.

"Even besides the performance issues, you don't want a multiplier on the cost of whatever you're using to manage those servers," Hochmuth says.

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Copyright © 2011 IDG Communications, Inc.

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