Re: [Xen-API] XCP really a VMWARE ESXi alternative?

[Mike McClurg <mike.mcclurg@xxxxxxxxxx>]

On 08/12/11 10:08, Scott Zupek wrote:
> I started trying with Xen Hypervisor (to run a small business(10 users) 
> mail (citadel) server, win 2k8 domain controller, web server (apache2 on 
> debian 2 or 3 domains) and remote support server (debian, w/ gnome)).

Since a lot of your email mentions confusion between the different Xen
variants, I'll start by quickly explaining the differences.

- Xen: this is the Xen hypervisor, the thing that makes virtualization
possible. It is analogous to an operating system kernel, such as Linux.

- XenServer: this is Citrix's paid-for Xen-based product. It uses the
Xen hypervisor, much in the same way that Debian "uses" the Linux
kernel. It also includes many nice management features, most open source
and some paid-for.

- XCP: this is exactly XenServer, except only the open source bits.

It makes the most sense to think of Xen as a being like the Linux
kernel, and to thing of XenServer, XCP, or Oracle's VM platform as being
different distributions that use the Xen hypervisor.

> Though the documentation was weak for just Hypervisor I was able to get 
> it running on top of Debian, but it was useless because I didn't have a 
> way to manage the host. (xen center, etc).  it seems that the entire xen 
> center application program is lacking support even on the paid Xen 
> side.. 

XenCenter is a Citrix product that is intended for use with XenServer,
and not necessarily with XCP. The XenCenter team is working to fix a few
issues with XCP/XenCenter integration, and hopefully we'll have better
integration with the XenCenter 6.1 release.

XenCenter does have good support on the "paid Xen side," which means
that if you give Citrix money for XenServer, they will give you support
for XenCenter and XenServer.

> I wanted to switch to XEN because it's more open source than 
> VMWare and I heard the performance is unbeatable.  But instead I ended 
> up with XCP Hypervisor (which still uses core xen hypervisor, correct?) 

Yes, see above.

> and now it seems, what shouldn't be much of burden on the systems, is a 
> massive burden on the systems. And I am left with nowhere to really turn 
> to.  My 1 hosted domain takes 1.5 minutes to load half my super easy 
> company webpage from the internet and it FLY's on the intranet.  Is 
> there some webpage that can help people that want to be able to diagnose 
> actual issues? 

This does sound like a configuration issue. You should have a look at
the XCP network throughput guide for more details:

http://wiki.xen.org/wiki/Network_Throughput_Guide

> Can't run the monitor/graph page in xencenter because it 
> fails due to some missing plug-in (im guessing since it actually doesnt 
> say).

Not a missing plugin. XenCenter was meant for use with XenServer; to
XenCenter, XCP looks like an ancient version of XenServer, and that tab
doesn't handle the error very well.

Try creating the file /etc/xapi_version_override and setting its
contents to "5.6.100" (without the quotes). This is a
mostly-undocumented hack to let XCP fake it's version number.

> Now a lot of this could be chalked up to my lack of Linux experience but 
> it seems like I would be the core audience (small i.t. consulting 
> business owner trying to make a name and lead by example) and the whole 
> thing ended up getting so confusing that XCP ISO /XCP core hypervisor 
> was the only option left.  this isn't what I wanted, but it was the only 
> way I could get my servers online.  Was this how this whole process is 
> intended?  I can't tell if XCP Hypervisor core thingy (looks just like 
> the vmware esxi hypervisor) is the main focus, if Kronos is the main 
> focus or running the Xen Hypervisor as a software app on a Debian/Linux 
> cli is the main focus.  Could be just me, but shouldn't this be 
> determined first before even 1 line of code is looked into?  I don't 
> mean to be a debby downer, it just seems like all 3 are bound to fail 
> because no time is dedicated to a "core" belief/program.

The "core" program is the Xen hypervisor, and there is a strong
dedication to this. Continuing the Linux kernel vs distro analogy, this
is akin to wanting there to be only one Linux distro, instead of the
dozens we have today (Debian, Ubuntu, RHEL, SUSE, etc.). The idea is
that you've got many options available to you, not that there is no focus.

I'm not trying to say that you're wrong for feeling this way, though.
This issue is something that comes up continually on the mailing lists
and IRC channels with new Xen users. It can be quite confusing. The Xen
community has recently tried to address this issue by creating better
documentation, and we've recently had two Xen Doc Days to inspire people
to write more documentation. It's a slow process though, and we've got a
lot of work left.

> I just saw a post regarding Kronos and if that is taking most of the 
> developers time, it makes me think I went the wrong direction with XCP.

I hope that this is not the case, but I understand where you're coming
from. We want to give people many different options for using Xen and
XCP, and we want to make it easier for people to adopt XCP and it's
XenAPI toolstack. Because of this, we decided to allow people to install
the XCP toolstack on top of Debian and Ubuntu (and hopefully other
distros as well). This effort also helps XenServer and XCP run on the
upstream Linux kernel and Xen hypervisor, and will hopefully make both
products stronger in the long-term.

As I said in a previous email, from which I believe you're quoting,
we're still committed to the original XCP appliance, and are working to
make that even better too.

Mike

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