A virtual private server can be described as the next step from shared web-hosting on the way to your own dedicated server. With server hardware becoming increasingly powerful (and affordable) in terms of CPU performance and memory, virtualisation is now playing a key role in the web-hosting industry. As a website owner, a virtual private server gives you many of the advantages a dedicated server offers, but at a fraction of the latter’s cost.
What are the key benchmarks of a virtual private server:
- physical memory;
- disk space;
- CPU allocation;
- operating system;
Physical memory (RAM) determines how many applications you can run on your VPS at the same time, and how many users can access these applications at the same time. This usually translates into “how many users can I have on my website without the site slowing down?”. Naturally, the more memory, the better. Keep in mind, however, that most virtual private server plans offer memory in the 512MB to 4096MB range. Anything below that range will not really let you do much except maybe run a proxy or a domain name server. Anything above, and you are well advised to consider moving to a dedicated server, not only because 4GB of memory will be rather expensive when allocated to a VPS, but also because a dedicated server still offers more performance than a VPS given the same specifications, and if your VPS already consumes 4GB of memory, the scales might begin to tip in favour of a dedicated server.
Most VPS deals offer anything between 5 to 40GB of disk space. Unless you plan to host a lot of large files (such as high resolution images, or media files), this space allocation should be sufficient. Keep in mind that more space will eventually become more expensive on a VPS plan than with a dedicated server, just like with memory.
Another key factor is the way CPU time is being allocated to your VPS. There are many different models, but all of them have one important caveat in common: make sure you enquire about the actual CPU being used in your VPS node. It makes a big difference whether your node is running an E3-1230 or an old P4! Below is a quick summary of the most common CPU allocation plans:
- A guaranteed cores plan gives you full control over the specified number of cores of the host’s CPU. While this method gives you the most in terms of CPU performance compared to other allocations, it is also the most expensive one since a large portion of a physical CPU’s computing time is reserved for you alone, whether you actually need it or not.
- MHz/GHz allocation guarantees you a certain amount of permanent CPU performance in terms of the CPU’s clock rate.
- Number of cores / fair share: this method gives you a certain number of cores of the physical CPU of your VPS node. If your VPS plan says “2 cores fair share” it means that you will be able to use 2 cores of the physical CPU for your VPS, and that you are allowed to use these two in such a way that you do not pose a problem for other clients on the same node also making use of these 2 cores. The exact definition of “fair share” depends on the provider you are with, so do make sure you read the small print.
- vCPU: this allocation is a mix of (2.) and (3.) – it might feature allocations such as “4 cores at 800MHz”, etc. Again, keep in mind to ask which kind of CPU is being used in your VPS node.
Most VPS offer less bandwidth or traffic than dedicated servers and are on a (sometimes shared) 100mbit/s connection, with some providers offering gbit/s as well, either by default or via an upgrade. It is tempting to get as much as bandwidth allocation as possible, but remember that anything too extreme is most likely just sales tactics. If you know how much traffic you will be using, purchase just as much as you need plus your growth estimate to avoid unnecessary costs.
Most VPS will be running any of the typical flavours of Linux, such as CentOS, Debian, Ubuntu, Fedora, etc. You are not limited to using Linux, however. Most providers will offer Windows based virtual private servers as well. These will, however, often come with additional licence costs.
The advantage of a VPS is its compactness – you can pretty much do whatever you could also do with a dedicated physical machine, but nevertheless enjoy the much lower cost of a VPS compared to paying for an entire server. The disadvantages of virtual private servers lie in their contention ratio and scalability.
The more customers hosted on a single physical machine, the more you will face increasing rivalry for a machine’s resources between the guest systems, such as I/O, memory, or CPU power. Scalability is another issue – you cannot scale up a VPS without ends. The current hardware of everyday’s high performing Intel or AMD architecture cannot be scaled ad infinitum, and a site requiring resources that were usually only served by dedicated servers a few years ago might even benefit from the additional performance (albeit at higher cost) from a dedicated machine with the same general specs such as CPU, memory, and disk space.