Agonizingly slow SATA HDD performance

[Gilboa Davara]

On Sun, 2010-09-12 at 18:12 -0400, Marcus D. Leech wrote:
> 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.
> 

Are you using AHCI or native IDE modes?
In-order to check it, check if there are ahci entries
under /sys/bus/scsi/devices/hostX/scsi_host/hostX.
(Where X is the port that's connected to your SATA drive.)

If you don't see any AHCI entries, reboot and go into your BIOS.
Locate the SATA configuration (Usually under peripherals or chipset),
and change it to AHCI. 

- Gilboa