Wiring up IDE devices

[galsterm at gmail.com (Matt Galster)]

On 8/7/05, Tom Metro <blu at vl.com> wrote:
> David Kramer wrote:
> > I usually wire my IDE chain like:
> >
> > IDE0M  Main boot hard drive, software, etc
> > IDE0S  Optical drive of some sort
> > IDE1M  Second hard drive, mostly data, apache documentroot, tmp, etc
> > IDE1S  Optical drive of some sort
> >
> > The theory is both hard drives should be on separate channels so they
> > can talk at the same time.
> 
> Sounds like a reasonable theory, but what I recall reading about IDE
> master/slave pairings is that it is better to pair fast devices
> together, as an optical device, which might require a slow IDE mode, can
> degrade the performance of a faster device on the same channel.
> Accordingly I've always paired my hard drives, and placed optical and
> zip drives on the secondary channel.
> 
> However, I don't have a lot of confidence in that recollection, and it
> may be based on faulty information. Has anyone else heard similar or
> conflicting information?
> 
> Also, given the oddities of IDE and the problems you can occasionally
> encounter with certain master/slave pairings, I wouldn't bet on this
> behavior being consistent. It probably is affected by which device is
> the master as well. Not to mention that the recommendation might have
> made assumptions about the IDE driver (such as assuming the behavior of
> the Windows IDE driver, which many not be applicable to the Linux IDE
> driver).
> 
> Conversely, the separate channels theory might similarly fail to provide
> a benefit if the IDE controller isn't capable of doing DMA to both
> channels at the same time.
> 
> Practically speaking, the only way to know would be to benchmark the two
> different configurations. Or, if you're really concerned about
> performance, buy a SATA controller for your hard drives and use
> SATA-to-PATA adapters. That'll also address your cabling complications.
> 
>   -Tom
> 
>

If you are really worried about performance, put each device on its
own cable.  The opticals being on their own can help if you are
burning or ripping a lot.

MEG