This is going to seem like a really really n00b topic and I appologize for that... I feel like I'm missing out on some fundamental understanding so I thought I would get some comparisons as to why one would virtualize with KVM vs. Xen. 

 

Grumpy has posted some fantastic guides, and I believe with my hardware (Supermicro X9SCM-F motherboard and Xeon 1230 CPU) I can run unRAID in a virtual mode.  The guides shown look like I can choose either path, however as I'm deciding which path I want to pursue, I would feel better knowing what some of the consequences are with either decision.

 

I suppose this is the part that I would explain what I want to do with my server.  I would eventually like to run a remove development environment (think iPython Notebook), as well as an operating system to handle Sab, CouchPotato, Sickbeard and so on...  I have no plans to run XBMC (perhaps try and run a headless version of XBMC so I can have my library auto-update?)

 

Regardless, my server is currently configured as a headless system, and I have no plans to change that setup anytime in the near future.

 

I'm glad there has been this mass interest, and published guides for making unraid run in a virtualized way... I hope this development keeps going!

 

Ogi

KVM and Xen both use QEMU to do machine emulation. That is where all the "magic" happens. There really is no difference in speed.

 

KVM Pros Advantages for Home Users:

 

1. KVM doesn't require you to boot into a separate kernel where as Xen does.

 

2. You do have to deal with installing / maintaining / upgrading a Xen package along with QEMU.

 

3. Speed wise you will not notice a difference between Xen and KVM.

 

4. KVM is slightly ahead of Xen when it comes to certain new features. For example, KVM running in a 3.12 Linux kernel can passthrough an nVidia Video Card when VFIO is enable in the Linux Kernel. Xen cannot do this yet but should have this ability in 4.4.

 

On an Enterprise Level there are some minor differences and advantages as to why you would choose Xen over KVM. In an Enterprise Environment you do not upgrade Linux Kernels (and doing so on 1,000+ Servers would be a total nightmare). However it's easier to upgrade a Xen Kernel and the Xen Package and roll that out (the "negatives" above are actually are positives). Plus some other management functions that do not apply to us.

 

For people who use KVM, upgrading the Linux Kernel (which includes new features / bug fixes for KVM) and QEMU (where the "magic" happens) is as easy as typing "apt-get upgrade" (as an example). With Xen it can / does work like that but there is a few more things going on that you have to be aware of.

KVM and Xen both use QEMU to do machine emulation. That is where all the "magic" happens. There really is no difference in speed.

 

KVM Pros Advantages for Home Users:

 

1. KVM doesn't require you to boot into a separate kernel where as Xen does.

 

2. You do have to deal with installing / maintaining / upgrading a Xen package along with QEMU.

 

3. Speed wise you will not notice a difference between Xen and KVM.

 

4. KVM is slightly ahead of Xen when it comes to certain new features. For example, KVM running in a 3.12 Linux kernel can passthrough an nVidia Video Card when VFIO is enable in the Linux Kernel. Xen cannot do this yet but should have this ability in 4.4.

 

On an Enterprise Level there are some minor differences and advantages as to why you would choose Xen over KVM. In an Enterprise Environment you do not upgrade Linux Kernels (and doing so on 1,000+ Servers would be a total nightmare). However it's easier to upgrade a Xen Kernel and the Xen Package and roll that out (the "negatives" above are actually are positives). Plus some other management functions that do not apply to us.

 

For people who use KVM, upgrading the Linux Kernel (which includes new features / bug fixes for KVM) and QEMU (where the "magic" happens) is as easy as typing "apt-get upgrade" (as an example). With Xen it can / does work like that but there is a few more things going on that you have to be aware of.

 

Thanks for the direct comparison.  Looking at your guides (which are great btw, thanks for making/posting them), it seemed like KVM would be the way to go if I didn't have a headless machine, but as I did have a headless machine, I wasn't seeing much benefit.  Now I see the error of my ways

 

Thanks again

Thanks for the direct comparison.  Looking at your guides (which are great btw, thanks for making/posting them), it seemed like KVM would be the way to go if I didn't have a headless machine, but as I did have a headless machine, I wasn't seeing much benefit.  Now I see the error of my ways

 

I run / oversee countless headless virtual servers. KVM and Xen both work great this way. Just different commands for creating / deleting / managing VMs. Neither is better than the other I would say.

 

For example in KVM:

 

virt-install --virt-type kvm --name Ubuntu --ram 1024 /

--cdrom=/data/isos/precise-64-mini.iso --disk /tmp/precise.qcow2,format=qcow2 /

--network network=default --graphics vnc,listen=0.0.0.0  /

--os-type=linux --os-variant=ubuntuprecise

 

All makes perfect sense and self explanatory to me. However, I have Linux Experience and going to a prompt isn't intimidating. However for Windows / Mac users who rarely if ever go to command prompts that might seem like greek to them.

 

If you want to do use KVM or Xen command line, there are TONS and TONS of guides on creating VMs for Windows, Linux, BSD, etc. and their are TONS and TONS of examples too. Plus the documentation for libvirt (the tool you use to create / start / stop / save / autostart / etc.) VMs is top notch.