New system recommendations

I am about to take a system from testing into production.

The system is a combination oltp/bi (network monitoring platform).

We are currently inserting about 1 million rows per day, and will
increase to probably 5 million once it goes into full deployment.

The current test production server is running Windows Server 2003,
PostgreSQL 8.1.3.

Record insertion is done via an ODBC call to a stored procedure from a
Windows based host monitor.

In addition to PostgreSQL, the server also runs Apache/PHP for the GUI
which displays our dashboards with the querying and drill-down front
end..

It is currently running on a 3GHz Xeon HT, 2GB RAM, dual 72GB disks
running RAID 1. This server is a 1U without only 2 drive bays, so I
have a potential issue with drive space.

As a result, I will be moving the db server to a Dell 1650 with 3 146GB
SCSI drives running RAID 0. System is a dual processor, 1.2GHz, with
4GB RAM.

Due to the amount of record insertions being performed, record insertion
speed is paramount - also because excessive execution time will have a
side effect of causing the monitoring agent to go stale. Some of the
users have mentioned that I will get better performance running under a
*nix OS. We are mostly a Microsoft OS house, but also run FreeBSD. I
am considering deploying with FreeBSD 6.0. I was wondering if anyone
has benchmarks showing speed of execution of PostgreSQL 8.1.3 under
Win2003 and FreeBSD 6.0. Also, are there any caveats or items I should
be aware of if running under FreeBSD? Any issues when running under a
multi-processor kernel? Anything in specific which I should include in
the kernel build to give me optimum performance for running PostgreSQL?

Needless to say, I am a bit nervous of moving to FreeBSD since I have
not tested it in a production environment.

Any advice will be deeply appreciated.

Regards,

Benjamin