I have been looking around for some time for virtualization solutions for our school network. The primary reasoning behind this is that I believe that virtual machines provide a much easier method for disaster recovery. If you have a Windows Server virtualized (i.e. your Active Directory Domain Controllers) they essentially are all contained within a single file. This makes backing up the entire machine very straight forward, and would allow versioning of your backups. For example if your physical server went down, you can quickly move the backup of the Virtual Machine (VM) to another server and have it up and running in minutes. Also if you version your backups, you could backup the entire VM ahead of a major upgrade, and if it all goes horribly wrong, simply revert back to the backup.
Recently I have been using the free VMWare Server (old version 1.0.8, as I am not a fan of the new 2.0 web only interface, seems very laggy). It does what we need to virtualize a few servers. Basically allows me to run 4 servers on one physical server, and means they are easily backed up and moved if anything goes wrong. However VMWare Server needs to be installed as an application on either Windows or Linux. This means there is an Operating System (OS) already running and using up system resources which could otherwise be used by the VMs.
This is where “bare metal hypervisors” come in. They are the program required to run and create VMs, but can be installed directly onto a blank server. They effectively are the OS and virtualization program all in one package, but tend to be much smaller and more efficient than a normal OS. This is because Windows, Linux etc are general purpose, they have to be able to do multimedia, games, file access, internet and a whole manner of other things. The hypervisor is designed to one thing only and that is run Virtual Machines and run them well.
On this note I had been looking around for “bare metal hypervisors” for a while, to try and eek out some more performance for our servers. I had been looking at the free one from VMWare, ESXi, however to be able to use it effectively (i.e. not by command line only) you need to purchase relatively expensive management software.
Enter Citrix XenServer.
Today they have released their hypervisor for free. Out of the box you can use it with a management tool called XenCenter which is also free. This gives me all the functionality of VMWare but with the added bonus of using a bare metal hypervisor which means extra resources for my virtualized machines.
Another neat tool it has is the ability to add an ISO repository. We have a shared folder on our network with ISO images of all our important CDs, such as Windows install CDs. This means when you wish to make a new VM, you can simply select the install CD you need to use from the list in your network repository. No more hunting about for CDs, and no need to physically visit the hypervisor server.
The install process for XenServer is fairly straight-forward. Download the ISO from here (after filling in a short form), and burn to a CD (it is only 360Mb or so). Pop that into your server, and boot from the CD. Then just follow very simple instructions.
You will be asked for your location, keyboard preference, IP addresses and the likes. Simple stuff.
Once it has finished installing just fire up the XenCenter app (download from the same page as the ISO for XenServer) and add your server to the list. You will now be able to browse your new server and see its stats (CPU, Memory usage etc).
From here you can also create VMs, repositories etc.
Click here for a link to Citrix videos section, showing how to do many of the basic tasks with the server, nice short easy to follow videos.
Still testing the water with this one, but it seems to be an amazing piece of software, and remember ITS FREE!! So what have you got to lose?
