Fedora Core 2, Adaptec ASH-1233 pci ide controller ultra ata card

[James Wilkinson]

Mitch Wiedemann wrote:
> I have in my computer two hard disk drives (/dev/hda & /dev/hdb), and 
> two CD drives (/dev/scd0 (CDRW) and /dev/hdd (DVD)) connected to the 
> motherboard IDE controller.

I replied:
> That's not necessarily optimal: but you know that. I assume you've got
> them spread out better now?

Mitch queried:
> No, actually I didn't know that...  You mean for speed of data 
> transfers?  Put my HDDs on different cables?  Whaddaya mean?

OK: it's not as well known as it should be that (parallel) IDE isn't a
proper bus. Only one device on a cable can be "active" at the same time.
If you send a request to hda, you can't do anything with hdb until the
first request is over, around 0.01s later.

That's noticable by human terms: it's an aeon to the computer.

(Serial ATA can also only have one device on a cable active at any one
time. This is primarily because Serial ATA can only have one device on a
cable...)

What you do about that is up to you, and depends on how you use the
drives. Unless you have all of swap, /usr, /var and /home (at least) on
the same physical disk, I'd recommend putting the two hard disks on
separate cables.

Apart from that, if you rarely use two drives together, they can go on
the same cable.

I also asked:
> Any reason why you're still using ide-scsi for the CDRW?

and Mitch replied:
> Um. Ignorance?  That's how FC2 set it up.  and it works, so I haven't 
> changed it.  How should it be done differently?  What are the advantages 
> of doing it differently?

Under the 2.6 kernel, using ide-scsi for burning CDs is Officially Not
Recommended and not needed. To switch, take the hdc=scsi out of the
command line, change any symlinks in /dev, change /etc/fstab, and change
/etc/cdrecord.conf.

It means that you can just use /dev/hdc when burning CDs, and not have
to worry about Jörg Schilling's fake SCSI bus/dev/lun namespace.

This appears to summarise things pretty well:
http://programming.linux.com/programming/03/12/09/1341236.shtml?tid=40&tid=91

But if it's working for you...

James.

-- 
E-mail address: james | When computers emit smoke, it means they've chosen a
@westexe.demon.co.uk  | new Pope.  Unfortunately, they invariably choose the
                      | wrong one and immediately get condemned to
                      | nonfunctionality for heresy.  -- Anthony DeBoer