Backup causing poor performance - suggestions

PostgreSQL: 8.2.4

We currently backup all of our database tables per schema using pg_dump every half hour.  We have been noticing that the database performance has been very poor during the backup process.  How can I improve the performance?

Server Specs:

Dedicated DB server

Database takes up 8.0 Gig of disk space

2 Xeon 5160 dual cores 3.0

16 G of memory

Two disks in raid 1 are used for the OS, database and backups.  SAS 10,000 RPM drives.

OS: Linux AS 4.x 64 bit

shared_buffers = 1 GB

work_mem = 20MB

max_fsm_pages = 524288

random_page_cost=1.0

effective_cache_size=16GB

max_connections=150

All other settings are the default settings. 

I have tried doing backups to a second set of disks but the performance only improved somewhat.

Does anyone have advice on how to improve my performance during backup?  Would adding two quad core processors improve performance?

Thanks,

Lance Campbell

Project Manager/Software Architect

Web Services at Public Affairs

University of Illinois

217.333.0382

http://webservices.uiuc.edu