> 1) Ideally I would like the 9Gb disks to have a single large filesystem +
>    some swap. However I think the max size of a filesystem is limited to
>    2Gb - Is this still true ?

I've built large file servers using NetBSD for some years now.  NetBSD
has no problems with 9GB file systems (other than running fsck on them
can take some time).  You could even run ccd on a number of these
drives to get a really massive filesystem.  I have a NetBSD 1.2 based
system with two Adaptec 2940 PCI controllers and 13 9GB Seagate Elite
disks (and a 48GB DAT changer).  It's been solid as a rock for several
years.

> 2) Will 512Mb of memory break anything ? (I know I will have to tell the
>    kernel the true memory size)

Recent (1.3 or later) versions of NetBSD correctly autodetect how much
memory is in your machine.  In earlier versions you had to config a
special kernel to tell it if you had more than 64MB of memory.  I've
had lots of NetBSD machines with 256MB of memory.  I've never gone to
512MB because I've never needed to for the applications I was running.
You'll probably want to config a kernel that tunes NMBCLUSTERS to 2048
(for a busy network server) and NBUF and BUFPAGES so that they use
more than 10% of memory.

> 3) Has anyone any experience of a machine with this sort of configuration ?

See above :-)

> 4) Has anyone used any of the Supermicro boards e.g. P6DBS with the builtin
>    Adaptec Dual Channel UWSCSI ? or got suggestions for other suitable
>    motherboards (preferably ones with will take up to 1Gb RAM) I should 
>    point out that 'the management' would REALLY like to use a commercially
>    available box rather than me build one out of bits !

I've always stuck with Asus or Tyan motherboards with PCI card SCSI
controllers.  I think some of the earlier on-board SCSI controllers
were less capable than the PCI cards (due to fewer SCBs?  my memory is
kind of fuzzy about this).

I have little experience with FreeBSD, but I'm sure it's capable as
well.  Just read ftp://ftp.cdrom.com/archive-info/wcarchive.txt for a
description of a monster machine.

-- 
Brian Baird				Brig Systems, Pleasanton CA
brb@brig.com				+1 925 484 2457