Trend Wars InterviewEditor: Dejan Milojicic, dejan.milojicic@hp.com

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I n this installment of Trend Wars, I discuss cloud computing and OpenNebula with Ignacio M. Llorente and Rubén S. Montero,

who are the principal investigator and the chief architect, respectively, of the open source OpenNebula project. I’ve heard quite a bit from several HP customers and colleague technologists about OpenNebula, so I’m delighted to have had the opportunity to talk with them. The video is available at http://www2.computer.org/portal/web/computingnow/videos/trendwars.

Dejan Milojicic: Can you tell us a little bit more about OpenNebula — how it started, what was the motivation, and where you’re going with it?

Llorente: OpenNebula is a research project that we started five years ago as a management tool for the orchestration and configuration of vir-tual machines in the datacenter. The main aim of the project was to address challenges from busi-ness use cases in real-world conditions. Open-Nebula is now an open source project aimed at providing the most innovative features for the management of virtual machines and for private cloud computing.

Milojicic: What were some key technical choices you made that made OpenNebula successful?

Montero: I think that the key aspect is its archi-tecture. It allowed us to use multiple storage back ends such as LVM [logical volume man-ager] and iSCSI [Internet small computer sys-tem interface], and different hypervisors, such as VMware, Xen, and KVM [kernel-based vir-tual machine]. Also having a robust and thin core, which uses C++ combined with a scripting driver plug-in back end, allows people to mod-ify components to build their own plug-ins, for scheduling or VM placement, for example.

Milojicic: Who are the top users of OpenNebula?

Llorente: Most of the users are supercomputing centers that are trying to support new ways to provide access to resources. Hosting companies are also evaluating it as a new cloud computing model, and telecoms are using it to explore new business models. I think the best supercomput-ing example is the SARA supercomputing cen-ter in Amsterdam, which announced a couple of months ago that its HPC [high-performance computing] cloud is based on OpenNebula. The best telecom example is Telefonica, which was a partner of ours in many European projects and is now evaluating OpenNebula to provide new cloud computing services.

Milojicic: What are the types of services?

Montero: We try to think of the type of ser-vice that can be deployed on OpenNebula as a black box. We mainly support anything you can put in any VM, so an entity like CERN is using virtualization and OpenNebula for batch- processing services like LSF [load-sharing facil-ity]. The batch virtualization team at CERN has done a nice job virtualizing 16,000 VMs for batch processing. But as Ignacio said, for exam-ple, telecom operators are using OpenNebula to virtualize Web servers, mailing systems, and databases, that kind of thing. So I would say that Open Nebula is not restricted to an applica-tion domain.

Milojicic: Who do you consider your competi-tion, and how do you differentiate from them?

Llorente: From the perspective of functionality, our competitors are all the existing cloud man-agement tools. But from the perspective of the target user community, we mostly compete with

OpenNebulaA Cloud Management Tool Dejan Milojicic • Hewlett-Packard LaboratoriesIgnacio M. Llorente and Rubén S. Montero •  Complutense University of Madrid

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Trend Wars Interview

12 www.computer.org/internet/ IEEE INTERNET COMPUTING

other open source technologies for cloud computing. We have four main differentiating factors. The first is the functionality that we provide for cloud computing management. We provide unique features that have been developed in the context of international projects — for example, our approach for hybrid computing.

We don’t follow an open core model. We think that the cloud is an evolution of the datacenter, so from the beginning, our design principle was to build something flexible and open so that any datacenter could use its existing services to build a cloud. I think the other important difference is performance and stability. From the beginning, we tried to address business use cases in production environments. Scalability was a very important requirement. Most of our users run a very large-scale infrastructure, so for them, stability is the most important issue.

Milojicic: What is the largest instance running OpenNebula?

Llorente: We have users in research, in computing centers, and in indus-try. Users in research and comput-ing centers, they’re happy to disclose information about the internal details of the cloud. But we have many users in industry that don’t want us to say that they are using the technology.

Milojicic: What is the largest data-center that you have designed Open-Nebula for?

Montero: We started by trying to target very large-scale datacenters. The goal was to build cloud infra-structures with tens of thousands of VMs and thousands of physi-cal servers. That’s for the single instance. We also envision multitier architecture for datacenters so that different multicluster instances can corporate together.

Milojicic: Since you brought up the future, what is next on your road map?

Montero: We just released the 2.0 version of OpenNebula. It was a really big milestone for the project because the components we want to see in OpenNebula are now in place — for example, authorization, user identity management, and image management. The next steps would be integration and use case devel-opment. We want to see more use cases from people who are using Open Nebula. How do they use Open-Nebula? We also want to improve some of the aspects that we already have, like improved high availabil-ity. Or, for example, a graphical user interface, that kind of thing.

Milojicic: When you look back, what were the key enablers for the success of OpenNebula?

Llorente: I think it was mostly virtual-ization. To understand OpenNebula, we need to go back five years, before cloud computing was a tool for the orches-tration of virtual machines. When we started OpenNebula, for us, the role of the administrator of the infrastructure was very important. Cloud comput-ing was not only a way to provide a simple API, it was also a way to pro-vide an efficient and scalable tool for the orchestration of the datacenter. The API is important but not the most important thing. To show that, we implemented three different APIs: the OGF [Open Grid Forum] OCCI [Open Cloud Computing Interface], the EC2 query API, and the vCloud API. Other APIs can be implemented because what we developed is API agnostic. We didn’t want to develop an open source implementation of a given API.

Milojicic: Is the fact that it’s open source helpful to you?

Montero: Community, for us, is quite important. Personally, it’s been

really encouraging working with people around the world submit-ting feedback, giving their opinions to us. It’s really very stimulating working with the community. For the technology itself, we are very happy that the OpenNebula commu-nity is so active. They send feedback through the mailing list. They send bug-fixing patches for the source code. They send future requests. The community is very, very important.

Milojicic: When you look back, would you do it differently if you were doing it today?

Montero: From a technical point of view, I’d say we’d do it just the same. As Ignacio said, the philoso-phy implemented by OpenNebula — keeping a toolkit for administrators so they can replace components — we really did well. And I would do it the same way. Probably there are minor things that we would do dif-ferently. For example, testing from the very first time when you develop software. That’s something that we incorporated later in the project because it takes a lot of effort. But technically, I think that overall the decisions were right.

Milojicic: Where do you need help going forward?

Llorente: I think we collaborate well with stakeholders in the cloud computing ecosystem. We col-laborate in the context of different working groups in standardiza-tion bodies. We provide feedback. We provide reference implementa-tion of the specifications. We also collaborate with many research groups in academia. For us, it’s an important source of innovation — they build many components around OpenNebula to complement the func-tionality that we provide. Industry is very important. We created the tech-nology to address the requirements

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OpenNebula: A Management Tool for Cloud Computing

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of business use cases, so we do not want to develop a technology just for research, but something that can be used in production environments and can address real needs from industry.

Milojicic: When you look at the cur-rent components of cloud computing, is there any single component miss-ing today?

Llorente: There are many research and technology challenges still to be addressed. We like OpenNebula because it’s not only a way to trans-fer results, it’s also a support to do research. This is a very interesting model because it contributes to the innovation of OpenNebula. We think that there is a research area in cloud enablement, in those components that you need to build the cloud. There is also a research area in cloud aggregation. We think that this is very important for the future of fed-eration of clouds. The main barrier to adoption is cloud interoperability, and it’s the main area that should be addressed.

Milojicic: Are you hinting at the need for standards? They’re tricky because sometimes they come too early and then they never mature, and other times, they emerge too late and de facto standards already exist. When do you think it’s the right time for clouds to bring standards?

Llorente: We have worked in the context of several earlier specifica-tions, which is good. But, of course, if you do not have adoption by industry of those specifications, they are not going to become a standard. It’s difficult to know when the right time is to define a standard. But in cloud computing, different interop-erability points are very important — for example, one of them is the public cloud API. Another is how to connect to the underlying infrastructure in

the private cloud. And the third one is the API that could be used for cloud bursting or cloud federation. Those are the main interoperability points, and we need standards for them.

Montero: I think that the prob-lem is that the cloud is in the very early stages of adoption. We are just finding out how people want to use clouds. How are they going to interact with the systems? That’s something that we are seeing in the standards groups we follow — sometimes they are behind the needs of the users.

It’s clear that there’s a gap between the discussions in the

working groups and the demands of the users. We discuss this in the context of different working groups, for example, to discuss a new functionality. But we cannot provide that functionality using this API because users want to keep compatibility with the API.

Milojicic: You provide services to users. Yet, when you look at hard-ware providers, you are their users. Is there anything that you would expect better from hardware ven-dors that can simplify your life? If your own users could develop service applications in a different way, would it help you in terms of scalability, reliability, and other aspects?

Montero: I think that in terms of hardware, we are mainly users of hypervisors, where the main gap is the interoperability between them and image format. For example, if

you have a VM running in VMware, moving that to Xen or KVM is dif-ficult. However, there are efforts out there. For example, the libvirt vir-tualization library provides you with an abstract layer to interact with multiple hypervisors at the same time. I think more efforts in that direction would be helpful for us.

As for people deploying services on top of OpenNebula or any other cloud management tool, I think that so far, we’ve been designing our services considering that the physical machine will always be there. With cloud computing, you have the ability to have an elastic infrastructure. You can add services

and remove servers at any time. So I would say to people, take that into account — build your service in a way that can add or remove resources.

Milojicic: What are the areas where you can expect help from others? What kind of research would you expect from academia?

Llorente: I think cloud computing is a computing model, and if you’re going to do research in cloud com-puting, there is an important over-lap with other research areas. You’re going to address challenges that have already been addressed at a given degree in other fields. We col-laborate with research groups in the field of real computing, for example, which is important for the federa-tion of different cloud sites. We don’t want to reinvent the wheel by per-forming research in areas that have been already addressed.

We like OpenNebula because it’s not only a way to transfer results, it’s also a support to do research.

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Milojicic: I’ve been asking you many questions. Do you have any answers for which I didn’t ask a question?

Llorente: The important message that we would like to communicate is that OpenNebula is the result of many years of research and development in cloud computing management and the collaboration with many important players in cloud computing. Also, that OpenNebula is an innovative technol-ogy that allows any datacenter to build a cloud using their existing services. These are the two important messages that we would like to communicate.

Montero: OpenNebula is the result of the effort of many people, and we really appreciate the effort of the engineers who have been work-ing with us, including Tino, Javier, Carlos, Jaime, and Daniel. Without them and their help, we couldn’t make this. We also really appreciate the community we have. It’s really

encouraging to us and a good per-sonal experience. So thank you to everybody using OpenNebula and making this possible and a reality.

F or much more on OpenNubula, the entire video is available for view-

ing online at www.computer.org/portal/web/computingnow/videos/trendwars.

Dejan Milojicic is a senior researcher and

director of the Open Cirrus Cloud Com-

puting testbed at HP Labs. He has worked

in the areas of operating systems, distrib-

uted systems, and service management

for more than 20 years and is an IEEE

fellow, ACM distinguished engineer, and

member of Usenix. Milojicic has a PhD

from the University of Kaiserslautern.

Contact him at dejan.milojicic@hp.com.

Ignacio M. Llorente is a full professor and the

head of the Distributed Systems Architec-

ture Research group at the Complutense

University of Madrid. His research interests

include advanced distributed comput-

ing and virtualization technologies,

architecture of large-scale distributed

infrastructures, and resource-provisioning

platfotrms. Llorente has a PhD in com-

puter science from the Complutense

University of Madrid and an Executive

Master in business administration from

the Instituto de Empresa Business School.

Contact him at llorente@dacya.ucm.es.

Rubén S. Montero is an associate professor in

the Department of Computer Architecture

at the Complutense University of Madrid.

His research interests lie mainly in

resource-provisioning models for distrib-

uted systems, in particular, grid resource

management and scheduling, distributed

management of virtual machines, and

cloud computing. Montero has a PhD in

physics from Complutense University.

Contact him at rubensm@dacya.ucm.es.

Selected CS articles and columns are also available for free at http://

ComputingNow.computer.org.

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