Re: [gentoo-user] Xen vs Citrix XenServer

[Michael Mol]

On Sun, Jan 1, 2012 at 12:40 PM, Tanstaafl <tanstaafl@×××××××××××.org> wrote:
> Thanks for your response Michael...
>
> On 2012-01-01 11:51 AM, Michael Mol <mikemol@×××××.com> wrote:
>
>> On Sun, Jan 1, 2012 at 11:18 AM, Tanstaafl wrote:
>> While I haven't played with XenServer, I have played with its
>> open-source clone, XCP, and was very annoyed by it. I'd rather run a
>> Gentoo dom0.
>
>
> I just thought that running a bare metal hyperviser would be more
> stable/reliable, and running it on a thumb drive would be much more
> convenient.
>
>
>>> First - I want to use a bare metal hypervisor that supports the
>>> following:
>>>
>>> 1. Can be installed on a USB FLASH drive (I have some Dell
>>> Poweredge 2970 servers with the internal USB slot for just this
>>> purpose), and
>
>
>> I don't think I've heard of anyone doing this, but I don't see why
>> it'd be a problem.
>
>
> Definitely not a problem for XenServer (although v6 isn't officially
> supported on a thumb drive yet), so I was mainly wondering about Xen
> itself...

XenServer is "just" the Xen hypervisor prepackaged with a custom Linux
distribution running in the dom0.

>>> 2. Fully supports both Windows Server 2008 (our Domain Controller),
>>> and Gentoo Linux (our mail and web servers).
>
>
>> The xen supports hvm, where it emulates hardware; in a full hvm VM,
>> *any* operating system comfortable on x86 should run.
>>
>> There's also paravirtualization, which is faster, and is likely what
>> you're thinking of wrt 'bare metal'. Signed drivers for paravirt
>> mode for hardware (such as your network, disk or system clock) are
>> available for current versions of Windows.
>
>
> Yes, PV is what I was thinking of, thanks - and apparently this wouldn't be
> a problem with gentoo either?

You'd want to either run xen-sources or another Linux kernel recent
enough to have specific support for communicating with the xen
hypervisor.

>>> I can't seem to find an ebuild for the xenserver tools, and when
>>> looking found out about Xen (I had thought that it went away a long
>>> time ago)...
>
>
>> * app-emulation/xen-tools
>>      Available versions:  3.4.2-r3 ~3.4.2-r5 ~4.1.1-r5 4.1.1-r6
>> ~4.1.2-r2!t {acm api custom-cflags debug doc flask hvm pygrub qemu
>> screen xend}
>>      Homepage:            http://xen.org/
>>      Description:         Xend daemon and tools
>
>
> Hmm... so will these tools work with XenServer? Or are they just for Xen?

xend is a daemon which runs in your dom0. If you're running XenServer
or XCP, you're running Citrix's custom Linux distribution in your
dom0. If you're running Gentoo in your dom0, you're not running
XenServer.

> Also, I ran across an article on the gentoo wiki that said that the VM
> images for Xen and XenServer are NOT compatible, which I find odd if
> XenServer is just Xen with some additional tools provided by Citrix.

Don't know. I can make any number of educated guesses as to why this could be.

> The article also said that the single biggest advantage of XenServer is the
> amount of time required to get something up and running - minutes for
> XenServer, compared to days for Xen - is this dated info, or still true?

It's analogous to running something like RHEL versus something like
Gentoo; there's a huge number of different ways you could do things in
Linux, but RHEL ties more of the pieces together for you than Gentoo
would. Likewise, XenServer ties more of the pieces together for you
than running Xen on top of some random Linux distribution.

[Drawing off my playing with XCP, the open-source clone of XenServer]

If you're going to use XenServer, you get most of a pretty interface
set up for you fairly quickly; the default console interface lets you
perform a variety of maintenance tasks through scripts and toolchains
that are already set up. (If I understand things properly, the backend
in question is the XAPI toolstack[1], for which there doesn't appear
to be an ebuild.)

[1] http://blog.xen.org/index.php/2009/11/03/xapi-toolstack-release-details/


>> * sec-policy/selinux-xen
>>      Available versions:  [M]2.20110726
>>      Homepage:            http://www.gentoo.org/proj/en/hardened/selinux/
>>      Description:         SELinux policy for xen
>>
>> * sys-kernel/xen-sources
>>      Available versions:
>>         (2.6.18-r12)    2.6.18-r12!b!s
>>         (2.6.34-r3)     ~2.6.34-r3!b!s
>>         (2.6.34-r4)     ~2.6.34-r4!b!s
>>         (2.6.38)        ~2.6.38!b!s
>>         {build deblob symlink}
>>      Homepage:            http://xen.org/
>>      Description:         Full sources for a dom0/domU Linux kernel to
>> run under Xen
>
>
> I though that xen-sources were no longer needed as of kernel 2.6.33+?

My understanding is that xen features are getting slowly reimplemented
in the mainline kernel tree, and that not all of the features are
there yet.

> Thanks again Michael,

IANAXE, but I'll happily explain my understanding. :)

-- 
:wq