Agonizingly slow SATA HDD performance

[Marcus D. Leech]

I have a new F12 system that is experiencing *agonizingly slow* SATA HDD 
performance, and I
   can't figure out why.  No errors messages at all, just *really slow*.

Mobo: GigaByte GA880GMA-UD2H
Memory: 8Gbyte 1333
Disk: 1TB Western Digital
CPU: AMD Phenom II X6 1090T

The system performance is generally pretty decent, except when it needs 
to do a lot of disk I/O,
   in which case, it's *really slow*.  I have other, much older, systems 
where similar operations
   (for example, a yum -y update) complete 5 to 8 times faster than on 
the "problem" system.
   I've noticed that if it's doing bulk disk I/O, the interactive 
performance of the system becomes
   horrible, almost like it's doing PIO to the disk and locking 
everything else out.

I'm doing an upgrade to F13 (via preupgrade) on the system right now, 
and after two hours,
   it's only about 12% complete.

I've seen *much* traffic about abyssmal SATA performance related to 
Ubuntu, but nothing
   much concrete relevant to Fedora.


-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org