Essentially, their underlying virtualization architecture may not have support for features like hotplug (which are used to enhance the memory/cpu/device resources assigned to a particular VM), or ballooning (used to take out memory resources from the VM), which operate at run time without the need of powering down the VM (i.e. providing a fully dynamic resource control on the VM instead of the need to allocate a new resource when the needs increase).

There is a lot more to it. If you are really thinking of a virtualized resource setup for your own business, I would strong suggest comparing different options before you stick on one. Perhaps you may be willing to add virtualization as one of your business portfolios (as a reseller, configur-ator, or just a consultant).

Let me know if you wish to connect to have more discussion on this. My URI will tell you where to reach me.