How-to understand what VPS is
 

It appears many people find it hard to understand what VPS is and how it works, so I just thought I'd make a small effort to explain a littlebit.

What does VPS mean?
Virtual Private Server

What is such a Virtual Server?
Basically VPS is all about running multiple Virtual Servers within one physical server.

What does Private refer to?
Each VPS gets its own portion of resources, which are usually guaranteed to be available to that particular VPS. For instance, the host server may have 8GB of ram, and 256mb (for instance) could be guaranteed to be available to a VPS. That would mean that regardless of what other VPS's on the same server use, that amount of RAM will be available to the VPS.

Also very important: each VPS runs completely independent of eachother. Each VPS has its own filesystem so a VPS can't see any of the data of another VPS. Also each VPS has it's own server load, can run its own Operating System, can be rebooted individually, and so on. Basically by the end user it can be treated as a dedicated server.

So does a VPS also have its own kernel?
Usually not, but it depends on the technology that the host uses.

Are VPS's truly 100% isolated from eachother, so no matter what happens they can not cause trouble to eachother?
Under normal circumstances, yes. However in extreme scenarios, VPS's can trouble eachother. For instance if the host server has a 100mbit uplink, and one VPS gets a 100mbit DDoS attack, then it makes sense that all other VPS's on the same server are also affected by it. It's up to the host to ensure maximum reliability by monitoring everything closely.

I mentioned VPS's on the same host server can each run a different Operating System. So could one VPS on the server run Windows, and another one Linux?
No, that's not possible. It is however possible to run different Linux distributions on a Linux VPS server. For instance one VPS could be running Red Hat Enterprise, and another one could be running Debian.

Is it possible to run anything on a VPS that would run on a dedicated server?
As long as it doesn't require kernel modifications, yes. (note: some technologies do support kernel modifications - that's not something I specialize in though)


For everyone who still has trouble understanding what VPS is, I thought of a nice example:

You could compare VPS technology to a block of apartments. The block has one roof, but under that roof there are multiple apartments. Each apartment has its own kitchen, living room, etc, so it can operate individually. Everyone goes in and out through the same door of the building though (VPS: traffic all goes through one network port). And I'm sure you can think of every other similarity.

Thank you for that, i have actually always wondered what it really means / does.

When you said everything goes through the same network port that is not always true because you can have more then one network card and that would help to regulate the amount of bandwidth that each is getting also because each network card could be connected to a different router and a different connection or connection speed.

Thanks a lot for that it help me a lot

Just remember if your going to buy a VPS make sure you get one with minimum guaranteed 256MB of ram. Other wise your probably going to run into performance issues.

Or more if you can afford it. Because I know I have 640MB of RAM in my server and almost all of it is being used for programs or cacheing.

Thanks.. I was really wondering this too

That would be absolute minimum I'd assume. 1GB would be even better :D

It can run on 256 but most of the time you'll run into issues there.. even 512mb can lag at times as well.

Thanks for pointing that out Ronin. I just made a edit to my post. Some times I get in a hurry and forget to proof read my posts. ;)

Thanks a lot! This truly helped. I was wandering what exactly VPS is - and this is a great topic and article. I really appreciate it.

I guess VPS is a vital thing for linux servers.

I would not really say it is vital. It is just that you can have many people on the same server but they can each change settings and everything because to them it looks like they are on there own dedicated server but it is really only 1 physical server. Lets say the physical server has 2GB of Ram and has 4 VPS. Then each person may be given 512MB or RAM alloted to them or it may be setup so one person gets more and others get less. Does this make more sense? If not let us know and someone will try to explain it in a different way.

MMeffert you lost me on this one. A VPS needs a minimum guaranteed 256MB of ram. If not as soon as the server gets busy it runs out of ram and starts using swap. And as soon as it runs out of swap, programs start crashing. Not too long after that happens the server stops responding. Once that happens your website is dead in the water. Please dont miss lead our users.

I am not trying to mislead anyone. I hope it did not look like I was. I was just using an example to help them understand it better. I was just using those numbers as examlpes. You could have 4GB of RAM and then each user gets 1GB or 2 get 512MB each and the other two get 1.5GB each. What ever is alloted to them out of the total amount of physical RAM.

Thanks very much for this. I have been wondering for VPS was. I always see it when I am looking for internet connections and other things like that. But I never knew what it actually was. This helped me out alot, thanks again.

Wow, while I was rading all the posts with Vp in them, I had no idea what it was. Now I know, great explanation.