subject: Save Money On Servers With Virtual Machines [print this page] When buying a new server, we have the task of choosing the pieces that will determine how the server will perform and how stable it's going to be. For instance a video gamer needs to be sure to get a very robust video card for handling graphic intensive games. On the other hand, a server should be able to fun at least a Raid 1 (Mirroring) disk drive setup to protect the data stored on the drives.
With Virtual Machines, the story is a little bit different. With virtualization technologies you have much more control on the resources you are going to assign to your servers, the cap being how powerful and fast is your virtualization infrastructure.
You may have a powerful server that is being used as a file server: probably its processor and most of its memory is underused. On the other hand, you may have a server that has many applications running at the same time using up all the CPU and memory to the point that it's performing poorly.
One of the things we need to let go is the assumption that our virtual machines need the same amount of resources as if they were physical ones. Do you need 4-CPU Cores on a Server that has no software optimized for multiple CPUs? Are you sure you actually need 8 GB to run those web applications running on IIS?
Enterprise Virtualization environments offer statistics and overviews on how our vm are actually performing. I recently installed a SQL Server environment from physical to virtual and they were really happy on how the new server / vm was performing: it had more cores and double the RAM (8 in this case). They were surprised when I told them: yes, you have multiple CPU cores and 8 GB of memory on that server, but I just gave it 1 core and 2 GB of RAM. They asked me why aren't we giving it more resources so it can run much faster? I then showed him the performance statistics on the vm and he was kind of surprised, the CPU was barely doing anything and the memory usage was only about half.
Now the client has more resources to create new VM's on the box that before could only hold just one. And the other benefits are even better.
For example VMware ESX is capable of optimizing the memory usage when you are running several virtual machines with the same operating system (Ubuntu LTS Linux for instance) by sharing the same memory blocks. How? Multiple VM's running the same OS share a lot of the same instructions in memory because they share the same code, so instead of running and loading the same code into memory several times, it does it just once.
Using this kind of performance monitors you can a better control on how your servers are going to perform, how much they really need and how much free resources you are going to have for future virtual machines.
