It will depend on what you need to do. If you want a couple of really high end machines to host a lot of little machines, then setting up a big machine as the host will probably be the best bet as you will only need one or two, instead of a lot of blades. As the vitalization software is based on the number of hosts, you'll want to reduce that as much as possible. Overall the power, cooling, rack space will depend on the number of machines that you need to vitalize, and how many machines you can vitalize in a single host.
I know that we have a single DELL 2970 running VMware server running 51 VMs, and we are going to be adding two more HP DL585s which are spec-ed out to run up to ~120 VMs. These three machines will take up a total of less than one half of one rack.
Hi there, in my opinion, if you are talking about virtualization and thermal and power savings, blades are your best answer. They are literaly a match made in heaven. If you are only running a few virtual machines, one or two rack mount servers are fine. But once you start growing past that then you can easily save by going the blade route.
HP makes a C-class enclosure called the "shorty". It's a C3000 enclosure. It is literally an infrastructure in a box because you can put server blades, tape blades, and even a SAN blade (HP's AIO) into it. That all fits into 6U of space. The C3000 is oriented towards the SMB market and is quite affordable. The C7000 is their larger enclosure for the Enterprise.
I have used the c3000 to greatly reduce the power and cooling in people's network environments.
You can get more info here: <a href="http://h20219.www2.hp.com/services/library/GetPage.aspx?pageid=546561&statusid=0&audienceid=0&ccid=155&langid=121">http://h20219.www2.hp.com/services/library/GetPage.aspx?pageid=546561&statusid=0&audienceid=0&ccid=155&langid=121</a>