linux-kernel - Re: PATA-disk named sda

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Message-id: <468E5420.7090605@shaw.ca>
Date:	Fri, 06 Jul 2007 08:39:28 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Christoph Pleger <Christoph.Pleger@...uni-dortmund.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: PATA-disk named sda

Christoph Pleger wrote:
> Hello,
> 
>>> In the newest Ubuntu Release, my PATA-disk is called sda instead of
>>> hda. Is that a general feature in newer kernel versions or is it a
>>> special feature in Ubuntu?
>> General. SATA and now PATA drives map onto the /dev/sd range as do
>> SCSI, USB etc
> 
> It seems to be not that simple, at least not if both the old IDE
> interface and the new libata interface are enabled as modules: In my
> Ubuntu system, I created two kernel packages (from the same kernel
> source and with the same configuration) and installed them. Afterwards,
> I re-created the initial ramdisks, one with the Ubuntu feisty utilities
> and one with Debian etch utilities. So, I had the same kernel with
> different ramdisks. With the Ubuntu ramdisk, my harddrive was named sda,
> but with the Debian ramdisk, it was named hda.
> 
> So, the name of the drive can depend on something which happens in the
> ramdisk environment. Does anybody know what that is? And is there a
> kernel command line parameter which restores the old behaviour?
> 
> And what about hdparm (setting 32bit I/O and multi-sector mode)? Suren
> wrote that 32bit I/O makes no sense when using DMA. Maybe that's right,
> but it does not correspond with my experiences. At least, I have the
> "feeling" that my IDE disks work much faster since I enabled 32bit
> support (DMA already was on before).

No, it has absolutely no effect in DMA mode.

Currently the DMA, multi-sector mode, etc. are not controllable with 
hdparm with libata. libata is designed to use the fastest settings 
possible by default. In a lot of cases this messing with hdparm was only 
needed because of stupidity with the old IDE code (like DMA not being 
automatically enabled if the low-level driver was built modular).

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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