What is Virtualisation?
Traditionally dedicated servers have been single tenant. You could imagine a dedicated server as being like a large building; it's big (powerful) and there's plenty of space (resources) for the family (website/database/mail etc) that lives there. This is all well and good, apart from the fact that there's wastage; the family rarely uses the building to capacity, except at Christmas when they throw a party. It gets worse; when they go on holiday the building still incurs running costs in the form of taxes and utility bills (electricity, cooling and maintenance) and still takes up the same space (datacentre footprint). In short; it's inefficient.
Wouldn't it be great if there was a way to reduce that inefficiency? This is exactly what virtualisation does. It allows the underlying hardware to be abstracted and decoupled so that multiple operating systems (OS's) can reside on top of it, each one seeing it's own CPU, RAM and hard drives, just as it would if it were a dedicated server.
What is a Virtual Private Server (VPS) then?
A VPS, sometime called a Virtual Machine (VM) is simply the name given to one of these partitions (or "slices") of a physical server, which is called a "host" to differentiate between the two.
It's virtual, as opposed to physical, because it's implemented on top of the physical server, it's private because each virtual server has it's own memory and storage that only it can access, and it behaves just like a dedicated server would do from the perspective of the user and system administrator.
Importantly, and unlike normal shared hosting environments, each user is compartmentalised into their own server; with their own OS, software, processes and policies. If one VPS is compromised because of poor security policy then it won't affect any other VPS on the physical host. Going back to the building analogy; a VPS is like turning the same sized building into apartments, where each tenant in the building conducts their business in private from the others, while still sharing the electricity, water, walls.
There are plethora of different virtualisation implementations and providers; most use a construct called a hypervisor as a layer in between the hardware and the VM's above. How the VPS technically achieves this doesn't really matter to a degree, what matters more is how this technology could affect you.
These concerns broadly fall into the following categories; Performance, Versatility and Security.
Performance
The extra layer of abstraction through the hypervisor means that a VPS performs slightly slower than a dedicated server of the same specification. However, a VPS will generally far outperform a shared hosting plan and some high end VPS slices can rival cheap dedicated servers for performance, and normally at a better price point as they're more economical for the datacentre to run.
If you decide to purchase a VPS be sure to check the specification of the physical hardware, after all this is what you'll be sharing. Normally in computing "more is better" but remember that the hardware will be divided up, so it's important to pay attention to the contention ratio i.e. the number of VM's the hosting company has placed on the host relative to it's power. If you are unsure, ask.
Versatility
Unlike shared hosting, where you are essentially sharing the OS with an unspecified number of users, you have a lot more control with a VPS. Webmasters can have full root access, change configurations as required, reboot services whenever they need, and install the OS, libraries, kernel tweaks and third party software of their choice.
A VPS is therefore more flexible than shared hosting, and as flexible as a dedicated server, but without the cost, making it a really useful service for those with more exacting requirements and for those wishing to try things out for themselves without taking too big a risk.
Security
Data security is paramount for many clients in the web hosting arena and businesses can be reluctant to host their data on a shared platform because of a fear of a server compromise. The extra layer of abstraction imposed by virtualisation and an independent OS means that a VPS plan should be more secure than shared hosting but it isn't as secure as a dedicated server because there is still an element of sharing going on. Security is probably the one of the 3 concepts we've talked about that relies on physical separation.
Summary
The arrival of the VPS opened a new "middle-ground" between shared hosting and dedicated servers in terms of performance, versatility and security. While prices always vary between providers, the VPS plan generally fits into this pattern on price too, filling the previously large gap between it's two siblings.
Virtual Hosting therefore offers a useful stepping stone for shared hosting clients before making the leap to a dedicated server. It could well make make sense for you if you're of intermediate to advanced technical skill and have outgrown your shared environment and need more of one or any of the 3 topics we covered.
If you do decide to take a VPS out scrutinise your options carefully and remember that you get what you pay for!
Stella Stevens regularly looks at different types of hosting plans such as VPS hosting, shared and dedicated servers. For more information, visit Krystal.
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