Virtual Private Server (VPS) Buying Guide

From a consumer of hosting services standpoint, in every respect except for the hardware components, a VPS using full virtualisation is the same as a dedicated server. Your decisions in respect to support, bandwidth and reporting are all the same and are discussed in depth in our dedicated server purchasing guide. So, in the VPS buying guide we'll only look at the factors which are very much specific to virtual private servers.

Type of virtualisation

Our overview of virtualisation provides an in depth look at the types of virtualisation technologies which are commonly used in hosting.

In summary there are two types:

  • Full virtualisation
    • Xen
    • VMware
  • Operating system virtualisation
    • Virtuozzo
    • Chroot
    • Free VPS

Full virtualisation allows your VPS to behave, from a configuration perspective, in exactly the same way as a dedicated server would. In operating system virtualisation, the installation and control of the server is more closely tied to and restricted by the configuration of the host server.

Virtual Servers which are deployed using operating system virtualisation are often cheaper as the underlying hardware requirements are often lower.

At Anchor we believe that full virtualisation is a better approach and have implemented our VPS offering using VMware ESX server. Learn why.

Resource contention

When you purchase a shared website hosting account, you are, as the name suggests, on a shared resource. There is no real visibility in terms of performance, contention etc. On the flip side shared hosting is very cost effective and dependence on services is often not as high as the type of application which lives on a dedicated/VPS environment.

On a dedicated server, you know that 100% of the memory, CPU and hard disc capacity is available to your application 100% of the time.

Enter the VPS environment; it behaves a lot like a dedicated server, but once again the hosting provider has the opportunity to contend (or over-subscribe) the resources. Your memory allocation and storage capacity are usually fixed, but CPU use and the rate at which you can read/write data to the disc (I/O bandwidth) are not.

An unscrupulous provider can make more money by overloading or under-specifying a server in terms of CPU and I/O capacity.

As a customer you have no real way of stopping this from happening. Your best to defence is to ask the hard questions at the time of purchasing and make sure you're satisfied with the answer.

In fairness, there are a lot of reasons why a hosting provider won't overload their VPS environment. The amount of money they save by not providing sufficient CPU and I/O compared to their total costs including co-location, staff, network costs, software licences shouldn't be enough to offset the unhappy customers and loss of reputation.

Questions to ask:

  • What are the specifications of the host hardware
  • How many VPS do they run from each host
  • Find out what the plan of attack is if you find the performance to be inadequate

Host hardware

The quality of the host hardware will determine the reliability of your VPS, so whilst hardware is not directly allocated to your server, you are ultimately dependent on the host server being operational.

One of the major benefits of a VPS is gaining access to high end hardware at a low cost, so make sure you're getting it. Look for:

  • Dual Hot Swap power supplies
  • Dual CPU's, preferably quad core
  • ECC RAM (it helps to prevent data corruption)
  • 15k RPM SAS HDD with hot swap drive bays

More important than the configuration of the host hardware is the presence of onsite spares. All hardware vendors only offer a 4 hour turn around on replacement parts, and that usually doesn't guarantee a fix within 4 hours. To be able to meet the common 99.8%+ uptime guarantees your hosting provider should be keeping a full inventory of spare parts on site for every component in the host server.

Upgrade options

One of the great benefits of a VPS is that you can add hardware resources easily. Adding memory or CPU shouldn't involve more than a simple reboot of your server. Whilst most people that start out on a VPS don't have a particularly demanding application, if or when it does grow it will be much easier to just keep adding more virtual resources than having to migrate onto a dedicated server. Make sure your provider has the capacity to allocation 4GB of RAM or more and 4 CPU cores or more to your server.

See also:

References/External Links

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