The Mystery of a Virtual Private Server

The private server concept has finally come of age, and has the potential to fill the gap between economy shared hosting and big budget dedicated hosting.

The concept is not a new one. The notion of dividing the resources of a physical server has been around for many years. Mainframes were once divided to allow more people affordable access to these large and very expensive devices.

So what is a virtual private server? It is more than a shared server and less than a dedicated server. A VPS simply put is, a server that runs inside another server. Each VPS looks, feels, and acts like a dedicated server but shares the same hardware. Think of it as a multi-tenant dwelling or luxury condo. Each apartment has it's own private entry, locks, electric, plumbing, bathrooms, kitchen and storage area within the same larger space.

There are a few companies that offer this product, such as Sphera, Ensim, and an open source project called FreeVSD. While Ensim and Sphera do not actually host anything themselves, they license their technology to many hosting companies around the world. Since my background is with Ensim I will be discussing this here.

Ensim Instant Server Technology allows a hosting provider to slice up a physical server into virtual or "private," systems. Each private server has it's own unique file system, disk space, user space (including virtual root), process space, CPU, bandwidth, and memory allocations:

Performance Isolation: Heavy traffic or CPU load has no affect on other private servers on the same box, but there are limits on CPU, Memory, and Process.

Functional Isolation: A VPS does not share applications or services with other private servers, nor do they share the same file system. Private Servers are invisible to each other and do not share processes.

Fault tolerance: Errors or faults in one private server do not affect others.

IP Addresses: Each private server has it's own set of IP addresses and network stack.

What do you get?
Root access to individual private servers: This allows you to run your own applications and fully manage your private server as you would on a dedicated server.

Guaranteed QOS/SLA: Memory, cpu, bandwidth, disk space, and uptime.

Enhanced Security: Private servers do not share disk space, TCP/IP stacks or processes.

Why do you need it?

In my experience managing and selling dedicated servers, I have found that users want a dedicated server for the following reasons:

Control: So they can install and run their own applications
Security: To ensure that they will never have to share the same space with other customers
Isolation: To eliminate the risk of downtime due to others mistakes, attacks/hacks or faulty scripts

Performance: Their site is growing and needs more resources.

All of these are valid reasons to graduate to a dedicated hosting account. What I've found however, is that most of these sites only utilize a very small portion of the dedicated machine: as little as 5% or less, which is where a VPS comes in. As we talked about earlier the private server gives you all the benefits of a dedicated server, but now you can share a physical server and still have the same guarantees of a dedicated server: for a fraction of the cost.

When you buy a private server you are paying for a slice of the server. You get a set of QOS/SLA values that can expand as you grow. Any of these values can be increased on the fly, and activated with a simple reboot of the private server.

An Example Private Server Plan:

5% CPU: Minimum Guarantee, you can't get any less but can burst to 100%
5% Bandwidth: Minimum Guarantee, you can't get any less but can burst to 100%
1GB Disk: Maximum Allocation but can be expanded
128MB RAM: Maximum Allocation but can be expanded

256 Processes: Maximum Allocation but can be expanded

Jumping from a shared hosting account to a dedicated server is like going from flying a single engine Cessna to a Jumbo 747. They do the same thing, get you from point A to B, but are very different in terms of their operating environment and required skill set. If you desire the speed, luxury, comfort and security of a Jumbo Jet but don't need to fly as high or carry as many passengers, then a Private Server is right for you.