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20030313: FreeBSD as a Unidata-supported platform

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: 20030313: FreeBSD as a Unidata-supported platform
  • Date: Thu, 13 Mar 2003 08:20:11 -0700
>From: Jim Koermer <address@hidden>
>Organization: Plymouth State
>Keywords: 200303121902.h2CJ2EB2009171 LDM FreeBSD mmap

Hi Jim,

>I've been trying to tell everyone for years (since 1996) that I thought
>FreeBSD was a great OS.

You were right!

>I'm glad it nearing adoption at Unidata.

We are very impressed with FreeBSD after running it hard on an amply
configured machine.  Right now, I am doing a stress test of LDM-6 on
our FreeBSD box: the machine has 10 inbound feeds and 50 outbound
feeds, mostly of the full CONDUIT datastream.  CONDUIT is the high
resolution model output from NCEP.  Its volume is roughly 75% of the
entire IDD volume for all other feeds including CRAFT (which is the
NEXRAD Level II/full volume scan data).  Relaying CONDUIT data is _the_
acid test for LDM performance, and our FreeBSD box is doing a great job
at it (but, so is our Sun Sunfire 280 SPARC box, thelma).  The bit
rates on our test machine are peaking at about 59 Mbps.  As a
comparison, our stress test of our Sunfire 280 (thelma), we ran it at
speeds averaging 54 Mbps and peaking at over 100 Mbps for several
days.  Doing the numbers shows that this is moving 520 GB/day of data
off of the server.  This was done without introducing any noticable
latency to the products!

>Here is what my ITS FreeBSD guru has to say about the memory map
>contraint that you mentioned:
>
>"I will look into the MMAP thing a little more.  The man page
>of mmap says there is a limitation imposed, however, I cannot find
>the limitation in the source code.  It could be that the limitation
>is not actually there anymore;  meaning that the issue was resolved
>a while back and just left in the manpage.   I have posted a Question
>about this to the FreeBSD mailing list to find out for sure.  I'll
>get back to you when the response comes."
>
>We'll keep you updated when we find out any more information.

We tried to get this to work, but stopped short of doing some code
modification after reading the mmap man page.  If you find that the man
page is out of date and there really is no limitation, I will be even
more keen on FreeBSD.  Since the Weather Service is now investigating
hardware for relaying all of the Level II NEXRAD data, it would be
_very_ useful to learn that FreeBSD did not have a 2 GB mmap limit.  If
it doesn't we will lean towards recommending a PC/FreeBSD solution
rather than a Sun/Solaris one.

Thanks for the input, and I will be eagerly looking for follow-up
information from you.

Tom