Stop Sharing Your Kernel: The Reality of Virtualization in 2010
If I see one more hosting provider trying to pass off an OpenVZ container as a "Dedicated Virtual Solution," I might just pull the plug on the rack myself. It is May 2010, and the Nordic hosting market is flooded with cheap, oversold containers masquerading as servers. If you are running a personal blog, fine. But if you are deploying a high-load Magento store or a critical MySQL cluster, relying on shared kernel virtualization is a recipe for disaster.
As systems administrators, we care about two things: predictability and isolation. When a script kiddie on the same physical node decides to run a fork bomb, your database shouldn't suffer. This is why at CoolVDS, we strictly rely on Xen Paravirtualization (PV). It is not the cheapest way to host, but it is the only way to sleep at night.
The Architecture: Xen PV vs. The Rest
Let's get technical. Most budget VPS providers in Europe use container-based virtualization (like OpenVZ or Virtuozzo). In this model, you aren't running your own OS kernel. You are running a "guest" inside the host's kernel. The overhead is low, which is great for the host's profit margins, but terrible for your stability.
Xen is a type-1 hypervisor. It sits directly on the hardware (bare metal). The "Dom0" (privileged domain) manages the hardware, while your VPS runs as a "DomU" (unprivileged domain).
Why Paravirtualization (PV) Wins
With Xen PV, the guest OS knows it is virtualized. It makes hypercalls directly to the hardware management layer. There is no binary translation overhead. We are seeing near-native performance on our CentOS 5.5 and Debian Lenny nodes.
Pro Tip: You can check your virtualization type instantly. Rununame -a. If you see something containing "stab" or "openvz", you are sharing a kernel. If you seexen, you are in a proper environment.
War Story: The "Steal Time" Nightmare
Last month, I audited a client's infrastructure hosted on a budget provider in Germany. Their Apache processes were hanging, yet CPU usage inside the VM showed only 20%. The culprit? CPU Steal Time.
In a shared kernel environment, the host scheduler was deprioritizing their container because a "noisy neighbor" was compiling code on the same node. We migrated them to a CoolVDS Xen instance. The result? Steal time dropped to 0.0%, and page load times improved by 400ms immediately.
When you buy 2GB of RAM on Xen, that memory is strictly allocated to your DomU. It cannot be burstable or stolen by another user. It is yours.
Tuning for Performance on Xen
Just because you have a dedicated kernel doesn't mean you can ignore configuration. In 2010, disk I/O is still the biggest bottleneck, especially with the transition from ext3 to ext4.
Here is a standard optimization we apply to our high-performance nodes to prevent the server from swapping too aggressively:
# /etc/sysctl.conf configuration for database nodes
vm.swappiness = 10
vm.dirty_ratio = 15
vm.dirty_background_ratio = 5This ensures that the kernel prefers keeping data in RAM rather than flushing to our 15k RPM SAS drives unnecessarily. Speaking of drives, while standard SATA is fine for backups, your production database needs the IOPS of enterprise SAS RAID-10. We are also beginning to deploy early-generation Enterprise SSDs for specific caching layers—the speed difference is startling.
The Norwegian Advantage: Latency and Law
Hosting physically in Norway isn't just about patriotism; it's about physics and compliance.
- Latency: If your user base is in Oslo or Bergen, routing traffic through Frankfurt adds unnecessary milliseconds. Pinging NIX (Norwegian Internet Exchange) from our Oslo datacenter returns single-digit latency.
- Data Integrity: Under the Personal Data Act (Personopplysningsloven) and Datatilsynet regulations, keeping sensitive Norwegian data within national borders simplifies compliance significantly compared to hosting in the US.
Conclusion: Choose Architecture over Marketing
Don't be fooled by "unlimited bandwidth" or "burstable RAM" offers. In the systems world, "burstable" usually means "unreliable."
At CoolVDS, we don't oversell. We provision Xen instances that act like real hardware. Whether you are running a heavy Java stack or a lean Nginx setup, you need resources that are actually there when the traffic spikes.
Ready to stop fighting with your host? Deploy a strictly isolated Xen instance on our Norwegian infrastructure today. Check your latency, verify your kernel, and get back to work.