My server load remains above 2.00 for several minutes while I am doing backups using a tar -czf command. If I move the tar files, the sever load gets above 4.00

Is there some way to make the backups take longer at a lower sever load? Perhaps the commands could be nice'd.

The load is due to the disk I/O. You could run the backup in nice mode as you have stated.

why don't you run backup at night.

my advices:

1. night backups
2. SCSI dual chanel controler
3. LVD disks

Regards
Peter