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Date:      Thu, 12 Feb 1998 16:50:50 +0100 (CET)
From:      Konrad Heuer <kheuer@gwdu60.gwdg.de>
To:        Vincent Defert <vdefert@trace.fr>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: FreeBSD vs Linux
Message-ID:  <Pine.BSF.3.96.980212162047.24814A-100000@gwdu60.gwdg.de>
In-Reply-To: <34E1DAF1.4A47@trace.fr>

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On Wed, 11 Feb 1998, Vincent Defert wrote:

> I am using an old version of Linux and I consider upgrading.
> FreeBSD seems to have a very positive image, but the same is
> true of Linux.
> 
> Could you please explain the main differences between them,
> and why people who tested both systems chose FreeBSD rather
> than Linux?

During the last months I spent a lot of time in comparing FreeBSD
(2.2.2-RELEASE) to Linux (2.0.30) on the same machine (P90) embedded in a 
heterogenous environment (DECalpha systems running Digital UNIX, SPARC
systems running Solaris etc.).

Major technical differences I found by a couple of performance
measurements and code studies are:

1. The Linux scheduler which is very different from other UNIX
schedulers (and thus the FreeBSD scheduler) behaves very poor when the
system is heavily loaded (no fair scheduling!).

2. The Linux NFS implementation doesn't compare to the FreeBSD
implementation. It's neither Version 3 as in FreeBSD nor does it support
write-behind by the nfsiod daemons. So for NFS clients which need write
access Linux is a bad choice (only about 1/3 of the FreeBSD performance).

3. Since the Linux 2nd Extended File Systems by default also buffers inode
and comparable data it's faster in operations like unpacking tar files.
With some risk one can mount a FreeBSD Fast File System with an async
option but then the dirty buffers containing critical data will be flushed
only in 30 second intervals. Linux runs a special bdflush daemon with a 5
second interval for critical data which is more reliable.
On the other hand I found the sequential writes and (much more important)
reads of larger files are about 30%..50% faster with FreeBSD and the FFS.

Last, non-technical point:

For people like me who are accustomed to UNIX for years FreeBSD is very
pleasing since it is in fact *UNIX* although it doesn't wear the
trademark. Linux is Linux and no UNIX - it's a reimplementation with a lot
of more or less perceptible small differences.

Konrad Heuer, GWDG, Goettingen, Germany
(kheuer@gwdu60.gwdg.de)


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