Hypervisor

In the previous article, I wrote about the hardware, now it is time to introduce the hypervisor.

This lab is hosted on Citrix XenServer, for free. Over the years, I tried many different hypervisor (exotic ones like Bochs or Virtuozzo), VMWare Workstation and Virtual Box, Virtual PC, Hyper-V and actually different flavours of Xen (does anybody still remember XenClient?). KVM somehow never made it to my labs, and I possibly forgot to list some others as well.

So why did I stick with XenServer?

1. It is free of charge. Just download it from www.XenServer.com, build your boot media and install it somewhere - XenServer has a hardware compatibility list, but will work on most hardware that I came across, including the occasional laptop computer (silent, portable and bringing their own keyboard and screen for local administration).
2. It can form a cluster (called "pool") of up to three machines, including HA, and the option to move VMs from one host to another.
3. Local storage is supported, as well as remote storage ranging from simple NFS shares to iSCSI and FC / FCoE SANs.
4. It can do snapshots, chains and trees, consolidation in the background, create new VMs from snapshots etc.
5. ISOs can be hosted on local or remote storage
6. XenServer supports the usual variants of networks - I usually have a private network which is available just on the host(s), an internet-enabled external network and a DMZ for hosting any VM that needs to be accessible from the internet, like this web server or a mail server. All three networks are separated and access is governed by a firewall which also performs as a router. I currently use IPFire for this job.
7. It can fully be administrated using a native Windows application, any SSH connection with the CLI and also using PowerShell commands, which is great for automation. I employ some scripts to mass-snapshot VMs and roll them back to their snapshots after I finished testing and breaking some stuff.
8. Also, for migrating to different hardware or locations or just for a backup, XenServer can store all VMs and their metadata on a single storage repository and can quickly import / reattach them on a new / changed host, preserving all snapshots, networks etc. - really useful for more flexibility or to quickly ramp up a new lab with a precreated / conserved one.
9. Lastly, XenServer can directly integrate with other Citrix products like the Machine Creation Service from Citrix Virtual Apps and Desktops or Citrix Provisioning Server.