[HCoop-Discuss] Our ideal architecture?

[David Snider]

Here's a quick crash course in virtualization for those who might not
follow:

There are 4 major kinds of virtualization:

Emulation - (Ex. Bochs) The virtual machine simulates the entire hardware
to run binaries from different architectures.

Full Virtualization: (Ex. VMWare, Linux KVM, Xen) Host machine used to run
guest binaries from the same "basic" (As in x86) architecture. The virtual
machine typically has a simplified instruction set to make the
virtualization process easier and the hypervisor does on-the-fly
translation of guest binaries. The OS can be unaware that there is any
virtualization going on.

Paravirtualization: (Ex. VMWare, Xen, User-Mode Linux) The hypervisor
exports a virtual machine that is similar to the underlying hardware. The
guest OS is modified to talk to the hardware through an Application Binary
Interface rather than directly to the hardware.

Operating System Level Virtualization: (Ex. OpenVZ, FreeBSD Jails, Solaris
Containers) The name "jail" that FreeBSD makes it pretty clear what this
does. Each server shares an underlying operating system but it is
partitioned in such a way to make it look and feel like it is on it's own
server. The advantage to this is that you don't have to duplicate a lot of
commonly shared resources. The disadvantage is that it is difficult to
control individual utilization of each server. (I.E If your web server is
getting hammered your mail server's performance suffers too.)

On Mon, 01 Jun 2009 19:08:18 -0400, Adam Chlipala <adamc at hcoop.net> wrote:
> Davor Ocelic wrote:
>> On Sun, 31 May 2009 09:23:48 -0400
>> Adam Chlipala <adamc at hcoop.net> wrote:
>>
>>
>>> Use Xen virtualization on both machines,
>>> so that we can create many virtual servers and move them among
>>> machines as needed.
>>>
>>
>> For our purposes, I recomend openvz virtualization.
>>
> 
> I can think of a few reasons why we might prefer Xen.  First, I think
> Xen is more popular, so it's more likely to have had folks spend time
> implementing features, and it's less likely to have bugs in established
> features.  Second, the less tight coupling of VMs seems like it should
> rule out some potential security problems.
> 
> I'm nowhere close to an expert on this subject, though.  I recognize the
> benefit of avoiding loading a separate kernel for each VM, and of
> avoiding the need to poke each VM to update the kernel.  I hope other
> folks will share their perspectives on the pros and cons of different
> virtualization tools.
> 
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