OpenVZ vs. True Isolation: A Sysadmin's Reality Check

Let’s be honest. Most of you buying a VPS in 2011 are looking at two things: the amount of RAM on the sticker and the monthly price tag. You see "1GB RAM" for $10 and you click buy. But if that slice is running on a crowded OpenVZ node, you aren't getting 1GB of RAM. You're getting a promise. And in the hosting world, promises are often broken.

I’ve spent the last week debugging a MySQL 5.1 crash on a client's "High Performance" VPS hosted by a budget provider. The logs were clean. Memory usage looked fine. But the database kept dying. The culprit? User Beancounters.

Understanding the architecture of your hosting environment isn't optional. It is the difference between a site that survives a Digg spike and one that 503s instantly. Today, we dissect OpenVZ.

The Architecture: Shared Kernels vs. Hardware Virtualization

To understand why your server feels slow, you have to look at the kernel. In technologies like Xen (which we use for our premium tiers at CoolVDS) or KVM, your VPS has its own kernel. You can load your own modules. You are isolated.

OpenVZ is different. It uses a single, shared Linux kernel for every container on the node. It is OS-level virtualization.

The Pros: Efficiency and Burstable Resources

I'm not saying OpenVZ is bad. It's actually brilliant for specific use cases.

• Density: Because there is no hypervisor overhead emulating hardware, we can pack more instances onto a single chassis. This drives costs down.
• Instant Scaling: Changing resources is a matter of updating a config file. No reboot required.
• Burstable RAM: This is the killer feature. If your neighbor isn't using their RAM, you can borrow it for a quick compile or a traffic spike.

The Cons: The "Noisy Neighbor"

Here is the nightmare scenario. You are hosting a Magento store. The guy next door (on the same physical server) decides to run a massive `tar` backup or a poorly optimized heavy PHP script. Because you share the disk I/O scheduler and the kernel, his load becomes your latency.

Pro Tip: If you are on an OpenVZ system, check your fail counts regularly. This tells you if the host node is denying you resources.

cat /proc/user_beancounters

If you see the failcnt column rising for privvmpages or kmemsize, your provider is overselling the node. You are hitting artificial limits even if `top` says you have free memory.

Why Local Matters: The Norwegian Context

Beyond the virtualization tech, physical location is paramount. We are seeing more Norwegian companies hosting in Germany or the US to save money. This is a mistake for two reasons:

1. Latency: A packet round-trip from Oslo to Dallas takes ~140ms. From Oslo to our datacenter in Oslo? <5ms. For database-heavy applications, that latency kills page load speed.
2. Datatilsynet Compliance: The Norwegian Data Protection Act (Personopplysningsloven) is strict. With the uncertainty surrounding international data transfers, keeping your customer data on Norwegian soil is the only legally safe bet for serious businesses.

The CoolVDS Approach: Honest Virtualization

We use OpenVZ at CoolVDS, but we do it differently. We don't oversell. When we allocate 512MB of RAM, we reserve it. We also monitor I/O wait times aggressively.

However, for mission-critical workloads, we recommend our Xen-based VPS platform or our new SSD-accelerated tiers. We use enterprise-grade Solid State Drives (Intel X25-E series) in RAID 10. The I/O performance difference compared to standard 15k SAS drives is staggering—we're talking about a 50x increase in random read IOPS.

Configuration Advice for 2011

If you are stuck on a legacy OpenVZ container, you must optimize your stack to lower the footprint. Ditch Apache 2.2 prefork if you can. Switch to Nginx 0.8.x and PHP-FPM. The memory footprint is drastically lower, keeping you away from those dreaded `privvmpages` limits.

# nginx.conf worker_processes tweak
worker_processes 1;
worker_connections 1024;

Don't let a shared kernel be your bottleneck. If you need guaranteed performance, low latency to the NIX exchange, and compliance with local laws, you need a partner who understands the stack from the metal up.

Ready to stop fighting for resources? Deploy a guaranteed-resource VPS in Oslo with CoolVDS today.