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
