There are many virtualization technologies some of them are free and many are with high price tag. We will limit or study here to just most commonly used types in VPS hosting business.
The main technologies in VPS hosting business are XEN,OpenVZ and KVM. We will give a small review from each type giving their Strong and weak points.
OpenVZ
pros: Direct Hardware access (very small overhead)
cons: No Kernel modification for GuesOS, No Windows Support
KVM
pros: can install almost any OS , excellent Harddisk access time
cons: bad network speeds in general,no advanced High availability and cloud support
XEN paravirtualized
pros: excellent network speeds, support very advanced features to allow cloud computing and high availability, kernel modification and Windows support (full virt with paravirtualized drivers)
cons: Virtualization layer decrease harddisk access speed
XEN HVM
pros: Can install any OS
cons: slower due to full virtualization