cdrom and cdrw

[Kerry Hoath]

I would assume you allready have ide hard disks.
If you have an ide drive on the primary master, and nothing on
the secondary ide channel except a cdrom I would jumper like this:
primary master hard disk. Most bioses will try booting primary master first
unless overridden so leave the hard drive there.
Secondary master, cdrw drive.
this will map to hdc as far as the ide driver is concerned and scd0 if
ide-scsi is active.
cdrom secondary slave.
this will show as hdd to the ide subsystem but scd1 if you have ide-scsi configured.
You probably want ide-scsi controlling both cdrom and cdrw since
cdparanoia and cdrdao work better with ide-scsi even with atapi cdroms.
You should therefore compile out ide/atapi cdrom support and in ide-scsi or compile both
as modules and put the right device aliases in conf.modules.
Better to just compile out ide/atapi support and in ide-scsi generally speaking.
Here is the output of /proc/scsi on a system with
both scsi and ide-scsi devices.
This system has a writer and a cdrom. The cdrom is controled
by ide-scsi but the writer is scsi. My other system only has
an ide writer in it controlled by ide-scsi.

Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: IBM      Model: DCAS-34330       Rev: S65A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 01 Lun: 00
  Vendor: IBM      Model: DCAS-34330       Rev: S61A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 03 Lun: 00
  Vendor: YAMAHA   Model: CRW8424S         Rev: 1.0g
  Type:   CD-ROM                           ANSI SCSI revision: 02
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: LG       Model: CD-ROM CRD-8482B Rev: 1.00
  Type:   CD-ROM                           ANSI SCSI revision: 02

Regarding simlinks, once you have your system configured with ide-scsi and/or
ide/atapi support and know where the devices will show up you create 2
links one called /dev/cdrom and the other /dev/cdrecorder.
Make sure you have 2 mountpoints and you can list both in /etc/fstab but
make sure to specify both noauto and ro so they won't automount at boot
and are mounted read-only something like this:
/dev/scd0 /cdwriter iso9660 ro,noauto 0 1
/dev/scd1 /cdrom iso9660 ro,noauto 0 1

Also make sure to set the environment variable CDR_DEVICE to the adapter/id/lun tripple
of your cdrecorder for example:
export CDR_DEVICE=0,0,0
that way cdrecord knows which device to use. You can also do it in cdrecord.conf
see manpages. There is also a cdrdao.conf where you
can set various options to tell cdrdao what driver to use,
what speed to burn at etc.
If using burn speeds faster than 16x and your chipset does not automatically enable
dma for the cdrecorder device you might want to do it on the
legacy block device with hdparm to prevent buffer underruns.
Even though my cdrw is ide-scsi, I do the following in startup scripts,
hdparm -d1 /dev/hdc
without this, the fifo undr cdrecord empties and smartburn
(It is a liteon drive) gets used to prevent coasters.
When I enable DMA for the cdrw the minimum fill rate for the fifo
is 90% and no use of smartburn required.
This is on a duron 750 with via udma/66 controllers, a 7200 rpm
quantum running dma and sustaining 15 megabytes per second transferr.
The i/o subsystem on this board is plenty fast enough for what is required
but the lack of dma causes grief for the relatively slow to respond
cdrw so I must enable it.

Regards, Kerry.
On Tue, Mar 26, 2002 at 10:52:16AM -0600, Cheryl Homiak wrote:
> I'm a little confused even after reading all the docs so I could use some help
> here.
> I have an ide/atapi cdrom, which I have loaded as scsi because i'm getting ready
> to get a cdrw in addition to the cdrom. Here are my questions:
> 1. Does placement of the cdrw and cdrom matter. The person installing wants to
> put them on separate ides as he says this can make the cdrw slightly faster.
> this means that one of them has to be hdb and the other has to be hdc or hdd (I
> would think hdc). Is it better to put the cdrw as single or primary and let the
> cdrom be the slave on my first ide?
> 2. Does this mean that i set up both the cdrom and the cdrw as scsi? I think I
> read that if you compile both scsi and atap/ide into the kernel the atapi/ide
> will take over which I don't want for the cdrw for sure.
> 3. If both are to be scsi, should my cdrw be scd0 and my cdrom scd1 or does this
> matter?
> 4. What symlinks do I do? Right now I have /dev/cdrom linked to scd0, but is
> this where the cdrw should be linked? Do I make an additional directory and
> mount point so that both can be mounte?
> Thanks.
> 
> 
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-- 
Kerry Hoath:  kerry at gotss.net kerry at gotss.eu.org or  kerry at gotss.spice.net.au
ICQ: 8226547 msn: kerry at gotss.net Yahoo: kerryhoath at yahoo.com.au