A simple matter of…

Today a friend^W aquaintance^W some bloke asked if I’d run Xen in production. My answer was “no, not really”. I do use it a fair bit, but I’m reluctant to but anything critical on it since I’ve had a problem a few times (as has this friend) where I received the dreaded “unable to communicate with backend device” error and the only fix appears to be to reboot the host OS. This is completely unacceptable. This error on occurs on starting (or in these cases re-starting) a domain, until that point it will be running just fine.

Anyhow, I then started thinking of all the different virtualisation productions out there (I’m only interested in Linux). I’ve tried to rougly group these, note that slow/fast are what I believe them to be - no testing has been done!

Pure software:

• Qemu - no hardware support required, very slow, open source
• UML (User mode linux) - no hardware support required, very slow, open source
• Bochs - no hardware support required, unbelievably slow, open source
• LGuest - no hardware support required, slow, open source
  

Sofware with acceleration:

• Xen (traditional software mode) - no hardware support required, paravirtualised, fast, open source
• VMWare Server - no hardware support required, fast, free but commercial
• VMWare ESX - no hardware support required, fast, commercial
• KQemu - no hardware support required, fast, open source
• Virtualbox - no hardware support required, fast, mostly open source, also commercial
  

Hardware based:

• Xen (hardware mode) - hardware support required, some paravirtualisation IIRC, fast, open source
• KVM - hardware support required, fast, open source
• VirtualIron - hardware support required, limited free version, commercial
  

Kernel based:

• Linux-Vserver - no hardware support required, fast, open source
• OpenVZ - no hardware support required, fast, open source version of virtuozzo
• Virtuozzo - no hardware support required, fast, commercial
  

Well at least that’s clear cut then!