For example, if your physical storage configuration supports volume sharing -- our own reviews were performed with an Emulex SAN storage switch and an Apple Xserve RAID disk array -- VMware’s VMotion option allows you to pause a running guest and start it up again on a different physical server. In a matter of seconds, you can push all the running guests and their applications from one server to another to take a machine down for maintenance. Or you can use VMotion for reprovisioning assets. A virtual PC that’s bogging down the network segment it occupies can be moved to a location with less traffic. No back strain, no recabling, and at most a few seconds of paused execution, not ended sessions or rebooting.
In environments with a mix of operating systems -- a common condition that turns even simple consolidation into a messy affair -- one solution would be to host each OS in its own VM. For example, on a PC server running one of VMware’s virtualization solutions, you can run any combination of Windows 2003 Server, Windows 2000, Windows NT 4.0, various flavors of Linux, and FreeBSD. You can even use VMs to host different versions of the same OS. Linux software is infamous for dependence on specific versions and vendor distributions of Linux. Virtualization is the only way to run applications designed for Red Hat 7.2 and Suse 9.0 simultaneously on a single server.
Virtualization is magnificent stuff, but it doesn’t jump out of the box and cure all ills. You can never create a virtual PC that outperforms the physical system underneath. You will learn much about your applications’ system requirements from moving them to a virtual environment. They’ll likely surprise you, either with how little of the original server they used -- that’s the typical case -- or how piggish they are. If necessary, you can throttle the nasty ones down.
And while one of the great benefits of virtualization is security -- it’s hard to accomplish much by cracking a system that doesn’t exist -- a virtualized PC can still be compromised. Fortunately, the cure is to overwrite the virtual PC’s disk image with one that’s known to be clean, but managing virtual servers still requires vigilance.
Ultimately, hardware consolidation is only one reason to opt for server virtualization, and it has wide appeal. Still, depending on each department’s unique needs, IT managers are sure to find innumerable ways that virtualization can benefit your enterprise. Too good to be true? Maybe. But it’s also too good to pass up.