Re: ide-scsi with 2 drives

[Robert Epprecht <epprecht@solnet.ch>]

Andrew Schulman <andrex@alumni.utexas.net> writes:

>> > > /dev/hda   hd
>> > > /dev/hdb   dvd writer
>> > > /dev/hdc   hd
>> > > /dev/hdd   dvd rom
>> > 
>> > I have found mixing hd's & cd'd on the same IDE  controller to cause 
>> > issues. I have even had issues with the position of the drives on the 
>> > ribbon cable, depending on the UDMA number of the device. I would start 
>> > with hd's on one cable  & cd/dvd's on the other. Make sure your chipset 
>> > is supported by kernel. This may be old info as I have been running 
>> > scsi mostly.
>> 
>> But then performance will take a hit.
>
> Not necessarily.  As usual, it depends on the usage pattern.

Exactly.  That's why I selected this unusual hw configuration.

As I said this is an audio workstation.  I wanted to have system and programs
on one hd and write my audio data to another one. I wanted to optimize them
for fast parallel performance.  Let's say I'm playing a softsynt which needs
thousends of audio samples from hda and writes the processed audio to hdc
while playing back some already recorded tracks (from hdc) to my headphones.
In audio work it's the worst case that counts: if a hd cannot deliver/write
the audio data fast enough there will be clicks or dropouts...

I use the dvdwriter only for backup (DVDRAM) the dvd reader for syncing
two DVDRAMs with important data. I don't care about speed here.

> An optical drive (slow) running on the same IDE channel as a hard drive 
> (fast) will slow down data transfer to and from the hard drive, when the 
> optical drive is operating (by forcing a lower DMA mode?).

Yes, but it can slow down also when it is *not* used when it's clock speed
on the cable is too low (as Alvin Oga mentioned).

> OTOH, if both hard drives are on the same IDE channel, then they may 
> compete with each other for the bandwidth on that channel.  So again 
> this can slow things down.

My main reason for choosing this layout.

> But if there's, say, one optical drive that you don't use very much,
> then pair it on an IDE channel with the hard drive that you want to get
> the most performance from.

I use *both* optical drives rarely and never during audio work.

Robert Epprecht