Interview with Dr. Moshe Bar

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.