Although I am somewhat of a new user of containers virtualization technology, I thought I’d write a short article giving an overview about using containers virtualization instead of dedicated physical servers for people thinking about trying virtualization technology – especially “containers,” or operating system virtualization technology. Here, I will address misconceptions that I had about containers and talk about how my perspective on this type of virtualization technology is changing.

Who am I? I am not an OpenVZ expert on containers virtualization or the open source OpenVZ software that I used. I am writing this while I’m still new to OpenVZ so I can represent a new user’s perspective. If you are just reading about containers for the first time, I am not that far ahead of you. This article is my attempt to give back a little to those who created this free open source software.

Why Use Virtual Servers Instead of Dedicated Servers
Like many of you probably, I must confess that containers virtualization never quite caught my attention until I decided I needed a remote name server and all I needed was enough of a server to run bind, but didn’t want to buy a dedicated server just to do that. So, I signed up for a virtual private server with a hosting provider for $80/year. The virtual server used SWsoft Virtuozzo software (the commercial “big brother” of OpenVZ) and it worked great.

In the process, however, I started understanding the containers virtualization concept and it became apparent that this technology is more than just a tool to create little servers. The way I see it virtualized containers can replace dedicated physical servers in many situations in data centers and do a better job, too.

Advantages of VPS
Most small dedicated servers are a waste of resources. People buy bigger servers than they need and the excess capacity is wasted. These servers take both space and power, which is expensive in a data center. Often, people don’t do any backups so after several years the hard drive fails and they lose everything. (Poor practice, but it happens.)

Imagine a rack of 16 Celeron boxes with 80 gigabyte drives being replaced by a Dual Core Athlox X2 with 8 gigabytes of memory and four 500 gigabyte SATA 2 drives running in a RAID 10 configuration. The server would cost about $2,000 to build and would only take 2U of space in the rack and use far less power than the 16 machines that it replaced.

Note that many of these 16 Celeron servers have idle time where the processor is doing nothing and they have lots of extra hard drive space that isn’t being used. By consolidating these systems, the free resources are combined, allowing you to run many more logical servers that each have more resources than the individual servers.

Ease of Setup
With containers virtualization, setup couldn't be easier as compared to building a dedicated physical server. All you do is type a few commands and the new virtual server is ready to go. Compare that scenario to setting up a dedicated physical server, which requires purchasing the server and software, setting it up, installing everything and configuring it. This involves additional cost and time. The virtual server is ready instantly and easily.

Backup Advantages
In addition, it is possible to run rsync scripts to back up all the virtual servers to external storage or backup servers without users on the server being aware that you are doing sophisticated backups. Then, it is possible to restore lost data easily.

Disk Space Allocation
On dedicated servers you have to install a big hard drive that is mostly wasted. If backups are needed, then it requires two hard drives. With OpenVZ, you just allocate space in the RAID array based on what is actually needed rather than what is allocated. The “allocation” is really just a software limit and that is a line in a text file that can instantly be changed the moment more space is needed. On a dedicated physical server, if more hard disk is needed, then it takes a few hours time to copy everything over and replace the drive – not to mention the down time.

Memory Upgrades
Memory upgrades are as easy as hard drive upgrades. Just one command, then the user has more RAM. But, what if the server is full and you don’t have any more RAM? No problem. Just copy the user’s virtual server over to another physical server with rsync and start it on the new physical server. In only a few minutes, the virtual server has been migrated to a new physical server and they are up and running.

Load Balancing
OpenVZ allows you to migrate servers live from one physical server to another. Suppose you have a server that is getting overloaded. No problem. You just move a virtual server to another physical server and problem solved.

Cost
The cost savings are rather obvious. An entire rack can be compressed into one or two servers. Picture the space and power savings, not to mention the greenhouse gas saved because you’ve significantly reduced power requirements. Think about the hours saved in setup and administrative time. When it comes to saving money, containers virtualization is definitely a winner.

The Down Side
Any time you add another layer of software, you have another layer of things that can go wrong. It takes some learning to understand the process. As virtualization develops, it will get better. OpenVZ is very stable and far less intrusive than other virtualization methods. OpenVZ is limited to Linux only so BSD and Windows users will have to do something else like possibly SWsoft Virtuozzo.

Conclusion
I have to say that my view of containers virtualization has radically changed. It is a different way of looking at the computing world and it takes some significant mental adjustment and education to grasp the big picture.

I believe that containers virtualization represents the future of computing. The space, power, and cost savings are too great to ignore. I see data centers that are massive clusters running tens of thousands of virtual servers that transparently migrate around the physical resources and are up 100 percent of the time. It will simplify dealing with backups, too. I think that every data center should be looking into virtualization technology now.