NFS RAID 0/5

Hi,

I have a web app using PostgreSQL which indexes, searches and
streams/downloads online movies.
I think I have a problem with NFS and RAID, it is not strictly
PostgreSQL but closely linked and I know
many people on this list are experienced with this technology. Apologies
if it is off topic.
Sometimes it is hard to not be the Developer, Database and System
Administrator all rolled into one.

I have a FreeBSD box with 1TB disk space RAID 5, 800GB is used.
This is mount via NFS onto Debian Linux running Apache/PHP/PostgreSQL.

I have a script which loads the directory structure etc. into the database.
As users surf the site web pages are generated by selecting from the
database as per a standard web app.
The server is on a 100mbit link and has reached up to 80mbits/s in the
past not using NFS or RAID.

The problem is when users start to stream/download the content the load
averages go through the roof.
Sometimes as high as 300.

I can only see mostly Apache processes running, up to 2000 is the max.
limit.
Even after 200 Apache connections the load avg. is over 10.

Could it be that using RAID 5 and NFS is causing the high load avg. on
the Linux web servers?
I have a machine with RAID 0 but not ready for a day or so.

I will soon need to move the databases onto the NFS partition and am
concerned it will increase my problem.

Any advise much appreciated.
Thank you.
Regards,
Rudi