Use Virtualization to Consolidate Lion Servers
Putting multiple Lion Servers (or Windows servers or Linux servers) in virtual machines on one computer takes advantage of hardware that may otherwise be wasted. This is known as server consolidation.
Many servers use only a portion of the capabilities of the hardware’s processor, RAM, and disk storage. A Mac Pro can hold 12 processor cores and 64GB of RAM, but few servers would take advantage of all this power. Info-Tech, a research firm, once estimated that most servers use 20 percent of their hardware capacity.
How many servers you can consolidate with virtualization depends on how heavily they’re used and how processor-intensive they are. You can run up to a dozen virtual servers on one Mac.
One Oregon school district replaced 44 computers running Mac and Windows servers with 7 Xserve computers running Parallels Server virtualization software — thus eliminating 37 computers. This move not only saved the district money in terms of hardware, but also saved money in reduced electricity and cooling costs.
Some of this cost savings from server consolidation is offset by the need for server hardware equipped with multiple fast processors and lots of RAM. You may also need multiple Ethernet cards in the server Mac to avoid a bottleneck caused by multiple servers accessing the network.
The big kibosh on server consolidation is Apple’s restriction to only two Lion virtual machines. But you can run other servers, including Snow Leopard Server, in virtual machines alongside your two Lion virtual machines.
For example, you can add a virtual machine running Snow Leopard Server or a Windows or Linux server to work as a Primary Domain Controller for your Windows clients, a service that Lion Server no longer includes. You don’t have to invest in additional computers.