Hello Fabian. Thanks again for your reply. I really appreciate you for taking 
the time.

I read what you wrote a couple of times, and (I think) it helped me to clarify 
some things. But still, I have a few questions and issues for which I am 
looking for a clear answer. I put them in bullets:

As I understand so far, OpenNebula has two types of users: the administrator, 
who basically has control over "everything", and the users, who can 
authenticate securely, instantiate some VM's, and do the work necessary for 
them. My question: can OpenNebula have another "layer" of users, some kind of 
"end-users"? What I mean is: suppose I, as a user of OpenNebula, using my 
created VM's, create a Web Service, which I publish on the Internet. Can anyone 
access this (someone who has no idea about the private cloud, someone who is 
simply accessing the URL), and by this way uses my Web Service (created on the 
VM's by the means of OpenNebula), so, basically, uses OpenNebula "remotely" 
(without knowing it)? Or this just doesn't make sense, since the whole idea of 
a private cloud is not to provide/publish information and services to the 
outside world, and this is not even possible since the virtual context?Are the 
most important reasons for installing OpenNebula
 the performance needs? Is there any other reason because of which I may want 
to install it, besides the fact that I might need multiple VM's (that I can 
manage) to perform a task (and to achieve platform interoperability)? I mean 
this has be the main point of it, right?When the load reaches its maximum (on a 
task which a user tries to perform on OpenNebula VM's), are new VM's created 
automatically (it the physical resources allow this) to support the performace 
needs? Or the only way of creating VM's is the "manual" one?Can OpenNebula be 
installed on any type of physical network, or does it have some special needs? 
Suppose I have an intranet in a company environment, with more interconnected 
physical machine that I'm actually going to use, does this change anything? Do 
I have to set up a separate physical network for the physical machines that I'm 
planning to include in the private cloud?


That's it for now, I don't want to ask for too much information all at once.:) 
I really hope that these questions are easy-to-answer for a professional, and 
will not take much time (for you Fabian, or for anyone else who thinks that can 
help me).

Thank you, and waiting for your response,
Biro Lehel.


--- On Sun, 12/11/11, Fabian Wenk <[email protected]> wrote:

From: Fabian Wenk <[email protected]>
Subject: Re: [one-users] application integration (service publishing) in 
OpenNebula?
To: [email protected]
Date: Sunday, December 11, 2011, 7:04 PM

Hello Lehel

On 11.12.2011 14:33, biro lehel wrote:
> what I've been referring to. I will have OpenNebula set up,
> and (as common sense would tell) I will have my application
> installed on the created VM's. My question only referred to:
> how can I install an application on these VM's (should I only
> just copy it, or is it more complex than this), or stuff like:

Look at the VM like at any other physical computer. It is just a container (eg. 
a virtual computer) where you can install the OS of your choice. The 
installation of your application inside the OS of your VM needs to be done the 
same as you would do it on a physical computer. But the installation of the OS 
in the VM needs to be done first. See my recent posting "Re: Creating virtual 
machines from scratch" [1] to this mailing list.

  [1] 
http://lists.opennebula.org/pipermail/users-opennebula.org/2011-December/007156.html

Look at an OpenNeubla cluster / cloud like on an additional abstraction layer 
between a physical computer and your OS installation.

An example:
If you have 3 computers, you can install on each one the OS of your choice and 
run it, but then you have only 3 concurrent running OS installation available. 
With OpenNebula you need to install Linux on all 3 computers (1x front-end and 
2x cluster nodes). The cluster nodes also need to support some kind of 
hypervisor (eg. KVM or XEN). Then you install OpenNebula on the front-end and 
then adjust the configuration for the shared file systems to be used by the 
cluster nodes. Then you can create VMs (virtual machines / virtual computers) 
and deploy them through the front-end (with Sunstone you also have a web GUI). 
Now you can create as many VMs as the two cluster nodes can support (depending 
on CPU power an available memory). You even can stop or terminate VMs and reuse 
them (with persistent image) at a later time.

> can the different tiers of the application (interface,
> business logic, and data repository) be on different VM's, but

Sure, they can.

> most importantly: how can an end-user (not the administrator,
> but a potencial client) use the application? Or there is no
> such thing as the "end-user / client" concept in OpenNebula,
> since the only user is the administrator who has control over
> the infrastructure? If OpenNebula provides IaaS support, I

In OpenNebula the administrator has full control over the running VMs, eg. he 
can stop (pause), resume or even shutdown / destroy them. OpenNebula also knows 
users, which eg. could create their own VMs (with their choice of OS 
installation) or can use pre-created shared system image to boot a VM. But as 
far as I know, out of the box OpenNebula is not able to provide virtualization 
on application level. But it has a very open and flexible design and you should 
be able to customize it to your needs, eg. with contextualization.

> suppose this means that he does not have control over the
> application only as a service, but rather he, as the admin,
> has control over the whole "physical" application?

What do you understand as "physical" application?

OpenNebula controls the distribution and monitoring of the VMs. It will place a 
newly created VM on a cluster node which has the requested requirements and 
resources available. It also manages all the system images (persistent and 
public / shared) and network interfaces (done through bridges) which the VMs 
need to run.


bye
Fabian
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