Книга: Fedora™ Unleashed, 2008 edition

Why Virtualization Is a Smart Idea

Why Virtualization Is a Smart Idea

The last few years have seen an incredible growth in the market for blade servers — high-performance, low-cost, space-saving servers that can be hooked together to form massive computing networks. These server farms provide a terrific amount of power for a relatively small budget, but the main problem with them is that distributing workload makes idle servers much more likely. For example, server A is a monolithic server: It has four CPUs, 4GB RAM, and so on, and runs both your database and web servers. If your database server is quiet but your web server is overrun with requests, it simply gives more resources to the web server. The downside here is that running multiple servers on one computer is insecure—a hole in your web server (hardly an uncommon thing) would also expose your database server. Now imagine that situation in which there are two servers: one running a database and the other running the web server. In this scenario, the database blade server would stand idle while the web server is swamped with requests.

If you think this problem is quite rare, you ought to know that experts estimate that current server farm utilization is as low as 15%, which means that 85% of your computers are likely to be sitting around waiting for something to do. Virtualization allows you to create multiple independent virtual machine (VM) operating systems that run on a single server. If one VM needs more processing power, the server simply allocates it more resources. More importantly, because the VMs are completely isolated from each other — they are literally treated as independent hardware — a security hole in one server cannot affect the others.

Moving your server farm from 15% to 80% or higher utilization either means your users get a much faster and more reliable service, or you suddenly have a huge amount of hard ware that you can sell or keep offline until needed. Either way, it is a huge cost savings, which makes virtualization the easiest way to cut your IT budget.

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