Interview with Dr. Moshe Bar

A conversation with the project leader of openMosix about its origins, its purpose and its future.

Behind openMosix technology, we can find the work of many intelligent and hardworking people. Recently, I had the chance to interview Dr. Moshe Bar, openMosix project leader, by e-mail. He spoke about his educational background, his interest in computer science and, of course, his work on the openMosix project. Here is the text of our interview.

Linux Journal: Please tell us your educational history.

Moshe Bar: My educational history is a B.Sc in math and an M.Sc and Ph.D. in computer science. I also am teaching at Tel Aviv University and the UN Atomic Agency. I am a permanent researcher at the Italian National Institute for Physics of Matter.

LJ: Were you first interested in math or computer science? How do you see the correlation between math and computer science, especially when you develop software such as openMosix?

MB: Everything is about math. Math is a formal language of symbols to describe our perception of reality and, by extension, the world. Algorithms are pure math. Programming is applied math.

LJ: What are your current interests?

MB: My interests are clustering, math, Harleys, chess and literature.

LJ: Do you think a programmer or software developer must have a formal education in computer science/engineering? Does this affect how a programmer thinks and solves problems?

MB: It certainly helps to know the fundamentals of computer science to be a good programmer. I started programming operating systems when I was 13, and I find that I now am addressing (with the same rate of success or failure, as you wish) the same issues as [I was] back then. I remember for instance back then, when I was a young kid of 13 or so, I was investing a lot of time in a good algorithm for generating non-colliding hashes. Today I am still fascinated by this subject and find that some of my algorithms from back then were not at all bad.

LJ: What was your goal in starting the openMosix project?

MB: I started openMosix because, as a prior project manager of Mosix, I could not agree to going non-GPL. I also didn't agree with how the project was managed by the co-manager at the time.

LJ: Why did clustering become an interest? Is it really difficult to create cluster middleware such as openMosix, considering the fact that few people or vendors create clustering software? What is your suggestion for developers who want to build a program similar to openMosix?

MB: Most "clustering" companies really are cluster management companies. The reason why so few do real clustering engines is it is difficult to do them well. A few dozen Ph.D.s were done on openMosix over the last 20 years, and it shows in the quality of the code and its efficiency during operation.

LJ: What is your experience as CTO of Qlusters, Inc.?

MB: My experience as CTO of Qlusters is open source gives you a lot of credibility in commercial environments and even can bring you clients. Most of our clients at Qlusters came to us because of my involvement with open source.

LJ: Your company, Qlusters, creates a great solution. Can you offer some overview of how ClusterFrame was created? Do you bring some technology from ClusterFrame to openMosix? Or has openMosix influenced ClusterFrame?

MB: The only shared component between ClusterFrame and openMosix is the process migration, which is the same code in both solutions. Everything else is different. ClusterFrame addresses business applications [such as] databases and trading systems, whereas openMosix addresses scientific applications.

LJ: Who are your idols? Do they influence your thinking, specifically involving openMosix?

MB: People who inspire me today are Pico della Mirandola (after whom the picometer is named), for his remarkable memory and good use of it. David Ben-Gurion, because he showed that even the most seemingly impossible dream can become a reality if enough people believe in it. I admire Paul Auster for his ability to write stories that somehow become personal to each reader, each story in a different way. I admire my parents for the hardship they endured to make me possible.

LJ: From the start until now, openMosix has grown fast. Many people have made contributions, including Matthias Rechenburg with openMosixView. How do you develop relationships with them? How do you manage the openMosix project with so many diverse talents? Do you give them any special direction?

MB: Managing programmers is not [the same as] managing bank employees. Each programmer wants his talents recognized and his/her ego massaged. That's mainly what I do as a project manager--I manage egos. And I set the overall strategic direction. I also do development work myself. It's much easier to get recognition from your developers if you yourself are a good developer.

LJ: openMosix is geared towards SSI (single system image), right? I see that openMosix faces two great challenges: implementing network RAM (aka distributed shared memory) and socket migration. What is the current status of each feature? Do you plan to recruit the MAASK group as a core openMosix developer, knowing that they contributed to the shared memory implementation? Can you explain your plan to implement gradually these two features?

MB: openMosix already is an SSI cluster. Network RAM will not make it more SSI than it already is, but I agree it would be a nice feature to have. DSM is a much more complex issue. It's easy to make DSM, but it is extremely hard to make good DSM. I would rather have no DSM than bad DSM. So, yes, I am interested in working with the MAASK group and others, and I hope they continue to send in patches. I will accept the DSM patch into openMosix the moment it is stable and increases the overall performance of an openMosix cluster.

LJ: PC clustering, we must admit, gained popularity when Donald Becker began experimenting with regular PCs at NASA, a project that came to be known known as Beowulf. What are your thoughts on Becker's efforts? Does Becker's work influence you when you are involved in a clustering project?

MB: I have talked to Donald a few times here and there. We have different spins on clustering. Actually, a lot of openMosix users run MPI or PVM (Beowulf) on top of openMosix, and they get along really well. I am sorry to see that his company (Scyld) didn't have the success he hoped for, but he is such a bright mind he can have success in other areas for sure.

LJ: Have you heard of or tried Compaq's Non Stop Cluster? It also started an openSSI project. Do you have any thoughts about the project? Do you plan to incorporate its algorithm into openMosix?

MB: Actually, openSSI uses parts of openMosix, which is perfectly fine. I am interested in what the project is doing purely out of academic curiosity. We do have contact from time to time, but we are not strictly related.

LJ: You also wrote Linux Internals. What was your mission with this book? Can you tell a little about your effort to write it?

MB: With Linux Internals I wanted to give experienced programmers [easy access] to the internals of the Linux kernel, without scaring people off. A lot of people liked the book for this reason. It was never meant to be an exhaustive kernel commentary, so people expecting that should additionally buy Prof. Bovet's book Understanding the Linux Kernel, 2nd Edition. I did contribute to his book as well, and actually I gave a speech to his class last year.

I also wrote three more books, and I am currently writing the 3rd edition of the extremely successful book OpenSource Development with CVS.

LJ: You have so many activities--lecturer, researcher, writer, developer, etc. How do you manage your time? Do you ever feel stressed with all of these jobs? What keeps you doing all of them?

MB: I certainly keep myself busy and don't have much spare time. But I like it this way; I like doing interesting things. I don't sleep more than four hours a day, and you can jam a lot of stuff into 20 hours if you are efficient about time. I have always tried to be very efficient with my time and have gotten used to it. I also travel a lot, and in those long hours in airplanes and airports I do stuff [for which] I don't need a phone, the Internet or a cluster. It works out quite well, really.

LJ: What is your relationship with the MOSIX team, especially Prof. Amnon Barak? I remember you were once a member of the MOSIX team. Do you still have discussions with them, perhaps sharing knowledge or innovations?

MB: We have severed all communication. Some of his students are contributors to openMosix, but that's all.

LJ: Several companies now are funding the openMosix project, including HP--what is your relationship with them? Do they also contribute to openMosix? Are there business deals between openMosix team and them?

MB: Relationships with commercial ventures, such as HP, are based purely on the idea that whereas they are full of cash, we are not. Therefore, I had the idea of having them give me a tiny little part of the cash to help out the project, that's all.

LJ: openMosix is starting IA-64 porting. What is your comment on the process? Do you think the porting will be smooth? How about porting to Opteron (AMD 64 bit)? How will you manage these two ports?

MB: We actually have finished porting to IA-64. We will now decide whether to port to Opteron or to Itanium 2. It depends on how much contribution we can get from either team.

LJ: openMosix is tightly integrated with Linux. In fact, the benefit each other quite a bit. Is there any plan to merge openMosix into official Linux kernel tree? How about porting to another platform, such as *BSD, Mac or maybe Windows?

MB: I don't want to merge openMosix into the kernel. I have talked about it with Linus, Alan Cox, Ingo Molnar and others, and I feel it is best to keep the two separate. I would love to port openMosix or part of its functionality to Windows. But I will wait for Microsoft to approach us with a proposal.

LJ: As far as I know, openMosix has become the number one open-source project in SSI clustering. What is your goal with this project? Do you want to keep it under the GPL? What would you say if someone wanted to start a descendant of this project, maybe use some part of openMosix technology as other SSI middleware?

MB: openMosix is indeed the number one open-source project for clustering, in terms of both installed base and growth. It will stay open source as long as I am managing it. If someone wants to fork openMosix, good luck with it. It's a lot of work to manage an open-source project, and the rewards are minimal.

LJ: Many people now use openMosix. Do you have a plan to write some technical documentation for it, maybe to explain process migration and its algorithm, the DFSA algorithm, in more detail? For example, I still hardly understand how process migration is implemented in openMosix's source code.

MB: There is a lot of documentation on our web site, and we explain the process migration there. I wrote several papers and articles about openMosix. The process migration is itself quite simple, we simply move the VMA from kernel to kernel and, on demand, move more VMAs. System calls are either shipped back home or executed locally, in some cases, if the files are locally available (DFSA). It doesn't get much more simple than that. The devil is in the details.

LJ: Cluster Knoppix, PlumpOS and Gentoo incorporate openMosix into easy-to-deploy packages. Is this purely the authors' idea, or do you have early talks with them? What is your perspective on these package? Any plans to make one of them an official partner of the openMosix distribution?

MB: I was aware of their efforts and helped where I could. Gentoo founder Daniel Robbins and I are good friends, and we talk regularly. No need to make any of them a part of the openMosix distribution, however, because we are not a distribution. They are distributions, and we are a part of them--it's much easier this way.

LJ: How does your family feel about your work? Do you talk to them a lot about your activities? Do you hope one of your children someday follows in your path?

MB: We have no kids so far; we got married last year. My family knows that I do something with a lot of public coverage, because they frequently write articles about what I do in newspapers in my country. But, they don't really understand what it is exactly. We talk about other things when we meet. The kernel is not a core interest for them.



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nice to know about such a

Anonymous's picture

nice to know about such a great personality

Re: Interview with Dr. Moshe Bar

Anonymous's picture

I've observed closely the openMosix development model and the workings... What I find is that there was no "new" code contributed by Bar. Some of the code is straight lifted from the MOSIX tree, after the fork. This holds him in very low credibility. I doubt if Bar can even code. He talks about contributing, but I don't see that happening. In fact, where do you look for contributions? Little or no talk about patches or features happens on the openmosix-devel mailing list.

Also, it seems the entire team that used to contribute, test, build packages, etc. is now replaced by a new team... may be Bar couldn't handle the ego of even one of them.

He doesn't also mention where he's done his PhD from, what specialization, where the thesis reports are, etc.

Show me the code

Anonymous's picture

Was openMOSIX *really* ported to IA64? If so, where is the code? It is not in the CVS, and the code is not to be found. Or was it just some exercise of some university course, which never proved to work, and was hidden before it got published?

Re: Show me the code

Anonymous's picture

You should check the patches section more often

Re: Show me the code

Anonymous's picture

The file that you can download if you follow that link - is 3 bytes long.

There is not a "IA64" port. It's only a link to a link to a non-existent path. He is lying.

Re: Show me the code

Anonymous's picture

when they say ported they mean that the code can now be compiled on IA-64 systems.

Re: Interview with Dr. Moshe Bar

Anonymous's picture

On what basis (apart from Bar claiming he deserves that) do people relate to him as a Dr.? Where did Bar do his academic degrees? what about? Where are Bar's thesises available from?
He has been asked these questions more than once, and simply avoided them!

Politico-religious extremism and open source

Anonymous's picture

I try not to do anything that profits Zionism or Wahhabism.

That is my choice and I do not wish to discuss it here with the various pro- and anti- zealots.

Unfortunately my government uses my tax dollars to support Israel and Saudi Arabia, so I don't get as much freedom of choice as I'd like! I donate as much as I can to the Palestinian Red Crescent as a small, futile gesture of penance.

Anyway, I won't pay for anything that Dr. Barr contributes to, since he's apparently an Israeli Zionist.

My money, my choice, not something I'm forcing on anyone else.

Re: Politico-religious extremism and open source

Anonymous's picture

what is zionism?

No one asked for your help

Anonymous's picture

The israelis are doing allot to support the OpenSource linux clustering. Both the people in the Hebrew Uni. and Dr. Bar are israelis. if you dont want to use israeli product you can also stop using Intel's processors because 10% of their R&D is in israel (the only major R&D center outside the US.)

Stop using the new Centerino (tm) processors that were developed only by the Israeli team in Haifa israel. Stop using microsoft windows because parts of it were developed by the Tel Aviv team. Stop using AIX because it's compiler and kernel was developed by the Texas team and the Israeli team. Stop using ICQ , developed by in israel.
Stop using the RSA. (The "S" is prof. Shamir of the hebrew Univ.)

You get the picture.

If you are a willing to invest in white owned buisnesses then good luck with that. We are living in the modern world and there is no place for descrimination and hate. I dont care who coded my kernel , I dont care if they are black or white. They are people , smart good hard working people. Get over it!

Re: No one asked for your help

Anonymous's picture

I am an American and am proud of it... When it comes to "Computers, Internet, OpenSource", I don't care where it come from as long as it follows the following criteria: It works, reliable, no violent security holes, and its free. I often give back to the OpenSource community. I agree with the statement above that the people involved in the OpenSource movement are smart, hard working, and forward thinking people.

By the way, I don't hate Muslims! I was in the Marine Corps for 8 years! Had a muslim roommate in college. Muslims aren't terrorists! Terrorists have varied backgrounds and ethnicities. What you don't see is that there is a difference between Islam and Terrorists.

The modern world is definitely global! May OpenSource Movement show the world that there is hope for the world to interact together in peace and harmony.

Re: No one asked for your help

Anonymous's picture

While there is a Prof. Shamir in the Hebrew University, the Shamir whose S is in RSA is from the Weizmann Institute in Rehovot.

Re: Politico-religious extremism and open source

Anonymous's picture

I'm a Moroccan citizen. I always appreciated Moshe's work but I
don't appreciate too much his web postings about arabs and
Most Israelis operating in open-source are friendly and pro-peace.
We even managed to work on joint BiDi enabling projects and
it is now borrowed by many hebrew and arabic projects.
I would like to ask Dr. Moshe whether he can accept one
day an invitation to Morocco to give a kernel talk or should I
stop dreaming ?
ps: one of my instructors in Morocco was Isreali citizen indeed.
and we don't have problems with this fact here.

Re: Politico-religious extremism and open source

Anonymous's picture

It may be worth noting that of all the major Arab countries, Morocco is the only one that still has a sizable Jewish population (several thousand), whereas the other countries expelled their Jewish citizens in 1948 and subsequent years, frequently without compensation.

Perhaps significantly, Morocco also is about as far away from Saudi Arabia and the Wahhabists as you can get.

Re: Politico-religious extremism and open source

Anonymous's picture

Good job openMosix is free then isn't it? And what's more, the GPL, and open source certified software in general, doesn't allow you do something like add a clause saying 'Not to be used in country X, by people Y, or application Z'. No politics there.

Re: Politico-religious extremism and open source

Anonymous's picture


The dogs are barking!

20 years of openMOSIX??

Anonymous's picture

It was MOSIX on which 20 years of academic research was done. 20 years of scientific work by Barak, Shiloh, LA'adan, Braverman, Amar, Keren et. al. Where is Bar's contribution to MOSIX? openMOSIX is just a recent fork of the work of giants!

Re: 20 years of openMOSIX??

Anonymous's picture

Almost for got to mention both Shiloh and Amar still contribute to the oM code base which grew out of the last GPL'd version of MOSIX. So yes I would say that oM can claim the same history.

Re: 20 years of openMOSIX??

Anonymous's picture

He was Project Manager for MOSIX. But hten you would know this if you read the interview.


Anonymous's picture

I had built the openMosix Cluster successfully and my cluster operate good. But when I configure openMosix, I didn't understand the NODESPEED option in /etc/openmosix/openmosix.config.
Please help me.

Cheer On!

Anonymous's picture

More cheerleading on the

Cheer on? SCO, this is ridiculous. We know it's you.

Anonymous's picture

Save yourself the trouble.

Re: Cheer on? SCO, this is ridiculous. We know it's you.

Anonymous's picture


The Dark side of open source

Anonymous's picture

The Dark Size of open source: Prof. Barak works all his life (literaly)
on MOSIX, and some youngster comes in, take the source code
and claim all the glory. All ofcourse under the pressure of VCs who
could care less about open source, fairness, honesty, or the scientific spirit.

Re: The Dark side of open source

chronicon's picture

Nice troll but please, get some rest!

Forks happen. It happens all the time. If you don't want someone to fork your "life's work" then don't ever issue your code under the GPL. It's that simple. Who doesn't understand this?

If you issue under the GPL and someone forks, you have no one to blame but yourself. Again, simple. There's no mystery there for the astute readers of Linux Journal. However, on the other side, proprietary licensing leaves everyone in the dark...

Now, if you desire community involvement, community support, bugfixes, patches, if you desire to "share the wealth" and generate interest in the project then the GPL works (and obviously in this case works very well) to the benefit of (if the article is correct) the largest installed userbase of any SSI clusters in the world.

Thanks Dr. Barr for CONTINUING the development of this GPL clustering system. Countless have benefited. And, thanks Linux Journal for an excellent interview and review of where openMosix is today and where it is headed in the future.

Why does venom always seem to come Anonymously?

Re: The Dark side of open source

Anonymous's picture

Is it just my impression or are the Comment Posts of every open source related web site being bombarded by proprietary software "simpathizers"? Why are they always anonymous? Isn't it a coincidence that it started after SCO decided to vilainize every Open Source advocate?

Re: The Dark side of open source

Anonymous's picture

What's so dark about it? Prof. Barak wanted to change the licensing of the project, maybe even take it proprietary. I have never heard it suggested that Moshe Bar is a gloryhound. He contributed to and managed Mosix with an understanding of the terms for doing so (GPL). It's some of Mr. Bar's life's work if you will. Prof. Barak wanted to change the license so Bar split. Simple as that.

It's been noted that Linus Torvalds is a pragmatist and not a politician. Richard Stallman gets hacked off about it in interviews every chance he gets. Torvalds has said in many interviews that the reason why the Linux kernel is GPLed is because he wants contributing developers to trust him. No one would have contributed to Linux if Linus could just change the license and then take all of the credit and all of the money. Once Professor Barak changed the license on Mosix, a number of developers ceased to trust him or even if they did trust him were unwilling to work under a different social contract.

Moshe Bar has not commited any sort of theft or taking. He excercised the rights the GPL conferred on him to continue working on his old project under the same terms he started working on it.

The other version of the story

Anonymous's picture

Well, this is the story as Bar presents it. But I heard another version: I heard MOSIX code was available freely, until Bar had the idea of making money out of the hard work of Prof. Barak and his colleagues. Only then did Prof. Barak change the license.

Re: The other version of the story

Anonymous's picture

There is alittle problem with your compliant. You see while Prof. Barak has made his tree proprietary, Moshe has left the oM tree GPL'd and free to everyone,including Prof. Barak to use.

Re: The other version of the story

Anonymous's picture

But then kind of stopped developping it, and focused on Qlusters' propriatary product (the one with all of those wonderful features).

Re: The other version of the story

Anonymous's picture

I heard MOSIX code was available freely, until Bar had the idea of making money

I can only reiterate Dr. Bar's statement: "It's a lot of work to manage an open-source project, and the rewards are minimal."
I would have no interest in Dr. Barak's work, were it not for the openMosix project.