pg_dump issue

Good morning,

I have identical postgres installations running on identical machines.  Dual Core AMD Opteron(tm) Processor 870 , 16GB RAM, Red Hat Linux 3.2.3-20 and 120GB worth of disk space on two drives.

Recently, I have noticed that my nightly backups take longer on one machine than on the other.  I back up five (5) databases totaling 8.6GB in size.  On Prod001 the backups take app. 7 minutes, on Prod002 the backups take app. 26 minutes!  Quite a discrepancy.  I checked myself than checked with our Engineering staff and have been assured that the machines are identical hardware wise, CPU, disk, etc. 

Question; has anyone run into a similar issue?  Here is the command I use for the nightly backup on both machines:

pg_dump -F c -f $DB.backup.$DATE $DB

Kind of scratching my head on this one....

Thank you,
Tim McElroy