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Adventures in virtualization


A few weeks back our school took ownership of a pretty powerful new server. We had budgeted for it last year, with the intent of getting it in the first term this year. After some issues with our supplier struggling to get all the quoted parts, we eventually got the machine fully working. It consists of 2xIntel Xeon 2.4GHz chips, 48GB Ram and 12TB of storage space on a dedicated Intel RAID controller. All of this is mounted in an Intel Pilot Point Chassis and a rack mount kit was purchased to complete the conversion.

The idea behind getting such a big server was to virtualize a number of secondary servers we have running for services such as FOG, BackupPC and FreeNAS, while also hosting our Exchange 2007 server. The existing Exchange server is a Pentium D era piece of kit, and while it has run very stably over the last 15 months, performance is terrible. The server takes forever to shutdown or restart, and its limited RAM hampers performance when lots of clients are connected at the same time.

We were left with 3 software choices for the host system: Citrix XenServer, VMWare ESXi and Microsoft’s Hyper-V implementation. All 3 are free, but differ in performance, supported guest operating systems as well as management capabilities. XenServer has a wonderful management console, but is pretty limited in which guest OS’s it will fully support. While you can run just about anything, it’s not guaranteed that the XenServer tools will run on the system or how good performance will be without a Xen aware kernel. My colleague and I spent two or three days fighting to get X running on a Debian guest to no avail. We had similar issues with Ubuntu as well. Most people would not run X on a server anyway, but in our case we need it for one application to configure internet sharing.

Hyper-V looked like a really interesting product, but we felt that the management tools were less useful in comparison to XenServer. I know that you can get far better management tools from Microsoft, but you need to purchase these tools, something our school doesn’t have the budget for. Since it is not part of the Microsoft School’s Agreement, we can’t get hold of the software that way either. That being said, I still want to look into this system further at some point and perhaps get a trial of the advanced management tools that are available on Microsoft’s website.

Last but not least, we looked into VMWare. It offers the widest range of supported guest OS’s by far and has plenty of other compelling features. That being said, I found the management console in Windows to be a slow affair, lagging when switching tabs. There’s also some limit regarding storage space in the product where you can’t have a local datastore larger than 2TB in size. I’m sure there are ways to work around this, but we were running out of time to experiment. We also decided that we did not want to end up breaking out 9TB RAID array just for VMWare. I know VMWare is a great product, but I feel it comes with a pretty steep learning curve for newcomers.

In the end, we went back to XenServer, having made the decision to switch to CentOS for running most of our Linux needs. Ubuntu is currently in experimental status in XenServer and I hope in time that it becomes a supported platform.

On Monday the server will be moved into our rack and additional VM’s will populate the new server. I’m excited to say the least, as it’s going to be an interesting learning curve managing so many VM’s.

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