Your choice of underlying virtualisation technology really matters.
Headlines from other VPS providers offering hundreds of megabytes of burst memory, along with simply fitting more VMs onto a physical server, do make it difficult to compete on raw figures for the price. However, those looking to buy a VPS really need to look at the technology they will be running on.
I'm happy to have found an excellent article describing the details between Xen (which we use) and Virtuozzo (which many competitors use). Read and be enlightened!
We currently use Xen as our virtualization technology. To put it simply, Virtuozzo (or the open source version OpenVZ) is one level above chrooting or BSD jail. Yes, Virtuozzo has much less overhead per VPS instance and has some performance advantages, but at a cost of isolation and reliability. Virtuozzo uses OS level virtualization, while Xen uses paravirtualization.
When evaluating the different virtualization technologies we had very specific requirements. We wanted virtualization technology that allowed for:
- dedicated server like isolation.
- customizations to the installed operating system (i.e. kernel, iptables, etc.) just like a dedicated server.
- proven deployment.
- cannot oversell services (ensuring a specific level of quality of service).
- complete separation of each operating system installation.
The differences with Virtuozzo and Xen are:
- fixed memory and disk definitions.
- custom kernels.
- firewall configuration.
- isolation.
For our purposes Xen acts, breaths, and looks like a dedicated server.
