A year or so ago, we at RouteYou bought a new PC to do data processing. Since we use all sorts of software, some running on Windows other on Linux, we decided to use virtualization for that one PC. It would give us the flexibility to let each developer pick the right tools for the job, and still be able to offload the processing to that one PC.
It all started with VMware Server installed on Ubuntu 8.04, but that turned out to be not such a performant solution. Then came the day VMware made ESXi free to use. After some hardware compatibility troubles we managed to get VMware ESXi running on our custom built PC. Life was good, thanks to better performance and easy administration through the excellent VMware Infrastructure Client. But we did realise that all that administration goodness would cease to be free of charge when we’d add a second virtual machine host. We would have to administer both machines seperatly, or buy some thousand dollars worth of licenses. Managing both physical hosts seperatly means you can’t easily move a virtual machine from one host to the other, whether the guest is running or not.
A month ago, the moment was there. A second processing PC was being ordered. We made sure it was compatible with VMware ESXI, but we had a wry sense about having to mis the flexibility of moving virtual machines around. So we started to look for other options and came across XenServer.
Both the free versions of VMware ESXi and Citrix XenServer have :
- Support for Windows and Linux guests
- Unlimited servers, virtual machines and memory
- P2V & V2V conversion
- Shared SAN and NAS storage
But XenServer adds some more features to its free offer :
- Centralized multi-server management
- Live motion
- Shared virtual machine template library
- Centralized configuration management
With VMware those extra options (not including live motion) would cost us around €1000 per physical server, which is almost the price of the hardware. So we started to experiment with XenServer to see if it could live up to the expectations. It didn’t take long before we started to see the differences between ESXi and XenServer :
- In VMware Infrastructure Client you can have different users, and assign them permissions to start and stop their virtual machines. That’s not possible with XenServer.
- With ESXi you can allocate more memory to virtual machines than you physically have available. They call it memory overcommit. Ofcourse this gets really slow when all that memory is actually used. So I find myself still wondering if the lack of this feature in XenServer is all that bad.