[Beowulf] Virtualization in head node ?

Robert G. Brown rgb at phy.duke.edu
Wed Sep 16 09:01:22 PDT 2009

On Wed, 16 Sep 2009, Tim Cutts wrote:

> On 15 Sep 2009, at 11:55 pm, Dmitry Zaletnev wrote:
>> When install CentOS 5.3, you get Xen virtual machine for free, with a nice 
>> interface, and in it, modes with internal network and NAT to outside world 
>> work simultaneously, witch is not the case of Sun xVM VirtualBox. Never 
>> used VMWare because of its value of $189, people say it's a good VM. But 
>> whatfor, if there is CentOS 5.3 with Xen, the industry best emulator/VM?
> VMware has some free versions; the pay-for versions have a number of extra 
> features which are generally missing from the competitors, and some of which 
> are quite shiny.  The automated hot migration of VMs to load balance, for

I'll also speak out in favor of VMware, as I use it pretty extensively
(and had negative experiences the first few times I tried Xen).  I
haven't tried what is it, KVM, only because of a lack of time and

The primary advantage of VMware at the server level is probably its
management interface, which is quite powerful and intuitive.  In the
latest server edition, it is web-based which gives you extremely easy
ways of performing remote server management.  I think it is an ideal way
of running Windows servers where you can't live without them -- put e.g.
Centos in a rock-solid, conservative, stripped, firewalled configuration
on a multicore multiprocessor big memory server, create as many Windows
Server VMs as you need and/or the machine supports, and you get the
ability to do pretty much anything you want remotely (such as "hard
reboot" a hung VM, checkpoint the VMs, stop the VMs and back up the
then-hard VM images, "freeze" the VM so that on a reboot it goes back to
the last pristine saved VM image, forgetting all the data and viruses
and so on that might have accumulated in the meantime) on a very stable
and secure base.  It also gives you some interesting ways of
accomplishing failover, as you can imagine, as the backed up VM images
are quite portable and can be moved around in a VMware server farm.
It's good for linux VMs too, don't get me wrong -- in fact, you can
download a whole bunch of "canned" preconfigured VMs for e.g. mail
server, web server etc. that only require you to boot them, adjust the
configuration to fit your local requirements, and you're done.  These
prebuilt VMs can easily be made into a sandbox, or put outside your
security boundary to do various chores with something even stronger than
a chroot relative to "inside" servers and clients, on a single piece of
hardware.  I just don't think it is possible for one to propagate from
inside a VM to the host OS or into other VMs, as everything is private
unless you very deliberately set up sharing; they are really separate
systems (although I'm guessing that somebody with root on the toplevel
system would still own the world, but who knows?).

But that's not where I use VMware the most.  It's "Workstation" product
is just awesome.  It gives you what I would argue is a SLIGHTLY BETTER
control interface to any or all VMs you might want to run on your
personal desktop or laptop.  I used to install Win/Lin dual boot against
the not-rare-enough times I absolutely had to use Win for something, and
of course this forces you to lose Lin.  It also made it difficult and
cumbersome to e.g. play Win games through an emulator or after a reboot.
It was wasteful of resources, and of course BOTH Win AND Lin want to
control the boot process, and getting a dual boot to actually work was a
pain then and remains an even bigger pain today, since Vista-of-Evil
doesn't want to play AT ALL nice in a dual boot environment -- I have
yet to get it to work although I haven't tried infinitely hard I admit
because I hate it anyway.

Now it is trivial.  Pop up the VMware console, boot up my XPPro VM and
who needs Vista?  XPPro will run forever on the virtualized hardware
interface as long as I can get linux to boot and run devices on the
toplevel system.  If I change machines, my XPPro VM can go with me
without all of the tedious crap from Windows Update and phone calls to
Windows service people that don't know what you're talking about or what
to do about it once they do.  Diablo II expansion, a click away,
snapshot/suspendable and resumable INDEFINITELY.  Various window apps I
have to have to work, sometimes, rarely.  I can also run Fedora and
Debian on the same machine in case I want to develop on both.  I can set
up a sandbox personal webserver on which to do web development without
exposing my personal data to cracking and theft.

Now for the bad news.  VMware has its own share of "problems" with e.g.
the rapidly varying linux kernel, and they are not always rapidly
resolved.  6.5.2 would only run under e.g. Fedora 11 with a tedious
patch and some flakes for most of its existence as a revision.  6.5.3
runs fine on Fedora 11, but the install RPM is broken and only a real
linux geek can ease it through an install (by hand-making the target of
the hung build script and then gently killing the hung steps of the make
until the script frees up and concludes).  I've heard of larger problems
with bleeding edge kernels.  For a server these usually aren't a
problem, but for workstations and laptops (far more likely to run one of
the dynamic, less debugged but more niftily tricked out distros) it can
be.  And yeah, it costs money, although Duke has a site license
(finally) so it won't cost ME money any more, or at least not much.  But
I've paid for a Workstation license out of pocket.  It's worth it.
Unless/until Xen or KVM or something else comes out with a similarly
powerful and tricked out console and ease of use and (still, overall)
reliability, VMware will be on my personal laptops for the rest of time.
It's just too useful a tool to live without, if you are a serious
computer geek who develops software, webware, does consulting, plays
games, needs multiple OS's but only want to carry one box and don't want
to have to reconfigure reboot to get to them.

"This message was paid for by the VMware corporation..." -- (not, just
kidding, kidding:-) which now owes me at LEAST a couple of free copies
of Workstation for the unsolicited testimonial that I would guess I will
receive when hell freezes over...


Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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