ACHI support

[Matthew Saltzman]

On Wed, 2007-08-22 at 17:57 +0100, Alan Cox wrote:
> >         Create /etc/modprobe.d/atapienable containing
> >         
> >                 options ibata atapi_enabled=1
> 
> This one shouldn't be needed, the default is atapi enabled since 2.6.18
> or so.

OK

> 
> >         
> >         Create /etc/sysconfig/mkinitrd containing
> >         
> >                 MODULES="ahci"
> >         
> >         to ensure that future kernel initrds will contain the ahci module.
> 
> Ah I was trying to work out why it didn't "just work" - your default
> initrd didn't have the AHCI driver. I thought 2.6.22 should be working!

Why would that be?  Does it have to do with the failure of the installer
to work with that controller?  Once I have it working for the current
kernel, will I still need /etc/sysconfig/mkinitrd?

> > 
> > - "hdparm -tT /dev/sda" doesn't show much difference in performance
> > between compatibility and AHCI modes.  Where should I expect to see a
> > performance difference, and are there any other settings needed to help
> > it along?
> 
> AHCI improves performance under load - the cost to issue a command is
> lower than with traditional IDE interfaces for one, and if your drive has
> NCQ support we can give the drive multiple commands at a time, and the
> drive is able to fulfill them out of order according to things like head
> position. As the drive has a list of work to do it can do it more
> efficiently based on its detailed knowledge of the media.

So not likely to see it in "normal use" on a laptop, then.

-- 
                Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs