SCSI Emulation problem

SCSI Emulation problem

[Agustín Herrera]

I've recently enabled scsi emulation (scsi emulation, scsi generic 
support, scsi cdrom support) for my cdrom and cd-writer.
Unfortunately, cdrdao and cdrecord take up all the processor's time 
when reading and/or writing to these devices. I've run hdparm on all 
devices and I've activated both dma and 32bit accesses.
I'm wondering whether this problem is due to bad configuration or it is 
just a linux-kernel issue (my version is 2.4.20).

SCSI Emulation Issues

[Agustín Herrera]

I am using scsi emulation (scsi emulation, scsi generic support, scsi 
cdrom support) for my cdrom and cd-writer.
cdrdao and cdrecord take up all the processor's time when reading 
and/or writing. I've run hdparm on all devices and I've activated both 
dma and 32bit accesses.
I'm wondering whether this problem is due to bad configuration or  it 
is just a linux-kernel issue (my version is 2.4.20).

Re: SCSI Emulation Issues

[Glynn Clements]

Agustín Herrera wrote:

> I am using scsi emulation (scsi emulation, scsi generic support, scsi 
> cdrom support) for my cdrom and cd-writer.
> cdrdao and cdrecord take up all the processor's time when reading 
> and/or writing.

Taking up all of the processor's time, or just locking up the system
while the processor remains (mostly) idle? The latter is more likely.

> I've run hdparm on all devices and I've activated both 
> dma and 32bit accesses.
> I'm wondering whether this problem is due to bad configuration or  it 
> is just a linux-kernel issue (my version is 2.4.20).

Do you have CD drive on the same IDE controller as the hard disk? 
Don't do this.

1. IDE operations "lock" the IDE controller for the duration of the
operation.

2. CD-ROM drives are *slow*. Much slower than hard disks.

A consequence of the above is that, if your CD drive is sharing an IDE
controller with a hard disk, accessing the CD will prevent access to
the hard disk for an extended period.

If you have a hard disk and a CD, make the disk the primary master
(hda) and the CD the secondary master (hdc). If you have two disks and
a CD, make the disks the primary master (hda) and primary slave (hdb),
with the CD as the secondary master (hdc). If you have three disks and
a CD, you need to buy another IDE controller.

-- 
Glynn Clements <glynn.clements@virgin.net>
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