The Past: One Application per ServerUntil fairly recently, data center operators typically installed just one application (or ”workload”) on each physical server. When taking into account development/testing environments and disaster recovery, a ratio of three to five physical servers per application was commonplace in data centers.1 Because of the “one workload, one box” approach, most servers run at a low "utilization rate" – meaning that just a fraction of their total computing resources are engaged in useful work. Even though the past decade has seen data center managers adopt server virtualization broadly, a 2014 study by NRDC found that average server utilization was still just between 12 and 18 percent.2 Show
Figure 1: Virtualization The Present: Many Applications per ServerA "virtual server" is a software simulation of a server and an operating system that executes programs just like a real server. Server virtualization offers a way to consolidate servers: it allows you to run multiple different workloads on one physical “host” server. Virtualization allows for fewer physical servers in a data center, with each remaining physical host server operating at higher total utilization. (See Figure 1, below.) Virtualization saves energy because a virtualized data center needs fewer servers to accomplish the same amount work as a data center using the one workload, one box approach. Although six is the average, it’s not unheard of to consolidate the workloads of as many as ten separate physical servers (or more) on one physical host server, so the energy savings can be substantial. Virtualization enables faster deployments, improves scalability, and reduces downtime. It speeds up disaster recovery efforts because virtual servers can restart applications much more rapidly than physical servers. With virtualization, you can move entire systems from one physical server to another in just a few seconds in order to optimize workload performance or to perform maintenance – all without causing downtime. Some virtualization solutions have built-in resiliency features, such as high availability, load balancing and failover capabilities.3 Big Opportunities in Small Data CentersThanks to compelling benefits, virtualization has become commonplace in large data centers. According to a 2016 Gartner report, on average most large enterprises report 75% or higher virtualization of their data center, "illustrating the high level of penetration," wrote Michael Warrilow, research director at Gartner.4 Virtualization is less pervasive in small data centers. A 2015 report by Techaisle found that server virtualization penetration had reached just 54% in US SMBs.5 This is mostly due to resource constraints: moving to a virtualized computing environment typically requires an upfront investment in software, hardware, and training. However, even the smallest data centers and server rooms are increasingly turning to virtualization to reduce operating costs, improve disaster recovery capabilities, reduce downtime, and simplify software development and testing. Savings and CostsVirtualization enables you to use fewer servers, thus directly decreasing electricity consumption. Reducing the number of servers in a data center also allows for a smaller power infrastructure. As a result, less energy is consumed by power distribution units, UPS systems, and building transformers. And because every server produces a lot of waste heat, fewer servers means that the data center needs less air conditioning. As a result of these indirect energy benefits, saving one watt-hour of electricity at the server level typically results in an additional 1.9 watt-hours of electricity savings at the facility-level!6 Note that some utility companies offer rebates to help offset the costs of virtualization projects. Please see the ENERGY STAR Utility Guide for Designing Incentive Programs Focused on Data Center Efficiency Measures for a (partial) list of utilities that offer rebates for energy-efficiency measures in the data center. Sample savings associated with server virtualization:
Table 1: Virtualization at Southwestern Illinois College: a 3-year Total Cost of Ownership Analysis Tips and Considerations10
For example, the exercise may yield a list of 100 "innovation" workloads that all reside in the same location. You can then determine the resource requirements for the entire group. In this example, you may just need 5 to 10 physical host servers to support the resource requirements of those 100 workloads.
1 The Economics of Virtualization: Moving Toward an Application-Based Cost Model, IDC, 2009. 2 Data Center Efficiency Assessment, NRDC, August 2014, p. 13. https://www.nrdc.org/sites/default/files/data-center-efficiency-assessment-IP.pdf (PDF, 485 KB) 3 The Economics of Virtualization: Moving Toward an Application-Based Cost Model, IDC, 2009. 4 Virtualization Market Now ‘Mature,’ Gartner Finds, InformationWeek, by Charles Babcock, May 16, 2016. http://www.informationweek.com/cloud/infrastructure-as-a-service/virtualization-market-now-mature-gartner-finds/d/d-id/1325529 5 SMB Server Virtualization Penetration Is Increasing But Challenges Remain, Techaisle Blog, May 7, 2015. http://techaisle.com/blog/197-smb-server-virtualization-penetration-is-increasing-but-challenges-remain 6 New Strategies for Cutting Data Center Energy Cost and Boosting Capacity, Emerson Network Power presentation, 2012, p.8. https://www.vertivco.com/globalassets/documents/blog/is03947_2012_energylogic_fin_62359_0.pdf (PDF, 1.4 MB) 7 Decommissioning as a Discipline: Server Roundup Winners Share Success, by Matt Stansberry, Uptime Institute, undated. https://journal.uptimeinstitute.com/decommissioning-discipline-server-roundup-winners-share-success/ 8 Implementing Server Virtualization at Southwestern Illinois College, by Christine Leja, 1/15/2010. c.ymcdn.com/sites/www.aitp.org/resource/resmgr/research/swic-server-virtualization-c.pdf (PDF, 162 KB) 9 How Cisco IT Virtualizes Data Center Application Servers, Cisco Systems, Inc., 2007. www.cisco.com/web/about/ciscoitatwork/downloads/ciscoitatwork/pdf/Cisco_IT_Case_Study_VMWare.pdf (PDF, 237 KB) 10 Section was developed using the following document as a guide: Using Virtualization to Improve Data Center Efficiency, Green Grid, 2009. Does a virtualized server uses less energy than a non virtualized server?Whereas CPU utilization for a typical non-virtual server is around 5% to 10%, for virtualized servers the figure could be 50% or higher. A server with a 50% utilization rate will draw about 20% more power than one at 5% utilization.
What is the difference between a virtual server and a physical server?While physical servers represent the tried-and-true, powerful data center deployment of the past, virtual servers offer businesses a cloud-oriented, innovative—and often managed—service for the future. At the same time, the decision isn't a clear-cut one.
What happens when server is virtualized?Server virtualization is the process of dividing a physical server into multiple unique and isolated virtual servers by means of a software application. Each virtual server can run its own operating systems independently.
What are the benefits to virtualized machines servers?Server virtualization brings positive transformations, such as reduced hardware costs, improved server provisioning and deployment, better disaster recovery solutions, efficient and economic use of energy, and increased staff productivity.
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