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Scaling and provisioning virtual servers

Michael Hayes | March 7, 2011
While virtual servers have proven a boon in the data center, they don't address the challenge of incrementally adding server capacity and automatically distributing load across them. As a result, the responsiveness and availability of a highly utilized Web application, such as Microsoft SharePoint, can deteriorate when the virtual machine it runs on is out of capacity.

The virtualization-aware ADC communicates through the hypervisor API to monitor VM resource utilization. This provides the ADC with real-time information about the virtual server instances, such as memory and CPU utilization. Combined with the ADC's application awareness, the ADC can load balance virtualized applications.

The ADC directs user requests to the best available server by shifting traffic loads away from slow-to-respond servers and by routing around down servers, highly utilized VMs or crashed applications. The availability, scalability and performance of the virtualized server environment can be further improved if the ADC can proactively modify the virtual environment based on the needs of the applications and users. This can be accomplished via an intelligent ADC control interface.

A virtualization-aware ADC control interface enables the administrator to create threshold conditions related to application performance and server responses. Combining these boundary conditions with two-way communication with the hypervisor API and now the ADC can trigger the hypervisor to make automated responses to application-centric events, such as load spikes.

For example, consider a hosting environment for a Web site selling flowers when Mother's Day is approaching and the traffic volume increases significantly. More VM resources are needed than normally were made available to the site. Load balancing alone will not mitigate the overloaded servers.

An intelligent control that has been set up to recognize the overload condition will trigger automatically and, via the intelligent platform management interface (IPMI), physically turn on additional real servers. The intelligent control then tells the hypervisor to spin up additional virtual server resources, which the ADC can then load balance to handle the load spike. This on-demand provisioning of additional VMs provides high availability and improved application performance to handle the additional load.

To achieve greater energy efficiency, the intelligent control mechanism can be used to set up triggers that specify if a server falls below a certain threshold of usage to stop any new traffic from going to it and when it reaches zero tell the hypervisor to move and consolidate VMs away from that server, and finally to power it down until it is needed once again.

The next step in identifying opportunities to further reduce servers, and reduce operational costs, is to identify what tasks hardware can do more efficiently than software.

Compression and SSL encryption are requirements for many applications. Mobile users, connecting via high-latency networks, benefit from compressed data delivery. Transmitting any kind of sensitive information over insecure networks such as the Internet requires deploying SSL and HTTPS encryption. Both compression and encryption place a heavy burden on server CPUs, whether physical or virtual.


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