The Truth About Virtualization: Why We Bet the Farm on Xen

Let’s be honest. If you have been in the hosting game for more than a week, you have seen the horror stories. A client's MySQL database crashes because a "noisy neighbor" on the same physical node decided to compile a kernel or run a massive backup script. The server slows to a crawl, load averages spike, and your pager goes off at 3 AM.

The culprit is usually the virtualization platform. In the race to the bottom on price, too many providers in Europe are stacking clients onto oversold OpenVZ nodes like sardines. They promise you 512MB of RAM, but it's "burst" memory—meaning it exists only in theory.

At CoolVDS, we take a different approach. We believe in hard resource isolation. That is why we built our infrastructure on Xen.

Paravirtualization (PV) vs. Hardware Virtual Machine (HVM)

To understand why Xen is superior for serious workloads, you need to understand how it handles the hardware. Unlike container-based solutions which share a single kernel, Xen offers two distinct modes.

Most of our serious deployments use Paravirtualization (Xen PV). In this mode, the guest operating system (domU) is aware that it is virtualized. It makes efficient hypercalls directly to the hypervisor, bypassing the overhead of emulating hardware drivers. This results in near-native performance for disk I/O and network throughput.

Pro Tip: If you are running Linux (CentOS 5, Debian Lenny, or Ubuntu 8.04 LTS), always stick to PV. HVM is useful if you absolutely must run Windows, but the overhead of emulating a BIOS and IDE controller will cost you precious CPU cycles.

Configuration That Matters

Many sysadmins are intimidated by Xen configuration files, but they give you granular control that other platforms lack. Here is a snippet from a standard production config file we might provision for a high-traffic LAMP stack:

# /etc/xen/production_db01.cfg
name = "production_db01"
memory = 1024
vcpus = 2

# Use valid block devices, not loopback files for better I/O
disk = [ 'phy:/dev/vg0/db01_disk,xvda,w', 'phy:/dev/vg0/db01_swap,xvdb,w' ]

# Networking bridged to the public interface
vif = [ 'bridge=eth0' ]

# The kernel for Paravirtualization
bootloader = "/usr/bin/pygrub"

Notice the disk directive. We map physical logical volumes (LVM) directly to the guest. This avoids the file-system-on-file-system overhead that plagues cheaper VPS implementations.

The Norwegian Context: Latency and Legality

Technology does not exist in a vacuum. If your target audience is in Oslo, Bergen, or Trondheim, physics is your enemy. Routing traffic through a budget data center in Germany or the US adds 30-100ms of latency to every handshake.

By hosting on CoolVDS infrastructure located directly in Norway, you benefit from peering at NIX (Norwegian Internet Exchange). We are talking about sub-5ms ping times to most Norwegian ISPs. For a heavy Magento store or a vBulletin forum, that responsiveness translates directly to user retention.

Data Protection Act (Personopplysningsloven)

Legal compliance is arguably more critical than raw speed. Under the Norwegian Personopplysningsloven (Personal Data Act of 2000), you are responsible for securing your users' data. The Datatilsynet (Data Inspectorate) is becoming increasingly strict about where sensitive data resides and who accesses it.

Xen’s strict memory isolation means that unlike shared hosting or loose containers, one customer cannot bleed into another’s memory space. It is a fundamental layer of security that helps you sleep better at night.

Why Storage Speed is the Bottleneck

CPUs have become incredibly fast. The real bottleneck in 2010 is disk I/O. A standard 7.2k RPM SATA drive can only push about 80-100 IOPS (Input/Output Operations Per Second). If you have ten virtual machines on a drive and they all decide to update their locate database at once, the server halts.

This is where hardware RAID comes in. We don't rely on software RAID. Our nodes utilize hardware RAID-10 with high-speed SAS drives. For extreme requirements, we are beginning to roll out Solid State Drive (SSD) caching tiers—a technology that is expensive but changes the game completely for database random reads.

The Verdict

You can save a few kroner a month by choosing a provider that stuffs 50 containers onto a single server. But when that server goes down during peak traffic, or when your I/O wait times hit 40% because a neighbor is running a torrent script, that savings evaporates.

Xen provides the isolation of a dedicated server with the flexibility of virtualization. It is not the easiest path, but it is the professional path.

Ready to stop fighting with resource contention? Deploy a Xen PV instance on CoolVDS today and experience the stability of dedicated resources backed by Norwegian infrastructure.