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Old 08-12-2003, 08:01 PM   #1
WanglessOlasov
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Question scsi, ide, atapi, what does it all mean?


Hey, i recently installed xcdroast for various reasons, and after configuring everything, it told me that i had told it to use atapi drives, and while this would work with my kernel, the support was still experimental, and i should instead use scsi emulation. I looked at the site, which gave me directions on how to do this, involving some lines being added to lilo.conf and modules.conf. I did what they asked, and reinstalled lilo, but after rebooting, i had absolutely no way of knowing whether or not the emulation thing worked. I believe i could figure all this out, but i'm not really a hardware person, and i just don't know what's going on.

Basically, could someone please give me a brief explanation of what it all means, including ide, the slave-master thing, atapi, serial ata, and scsi, and how to detect how it all relates to what i've got in my system? I'm really clueless here. (sorry, i just had to add that thing)

Thanks
 
Old 08-12-2003, 08:19 PM   #2
slakmagik
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Hm. Slave and master have to do with how your drives are jumpered or how they are positioned on the cables. More technical than that, I can't get.

IDE is Integrated Device Electronics, and scsi is Smart Computer Systems Interface or something like. I forget atapi. Basically, ata, atapi, ide, I think all mostly goes together. Basically, scsi is a more expensive faster controller due to the way the system interfaces with it - it has a sort of processor of its own. IDEs are driven by the system.

I have no idea why cdrecord insists on scsi-emulation. It's a pain. To find out if it worked, do 'cdrecord -scanbus' - if your drive is listed you should be good to go.

Not a guru answer, but maybe it's something. *g* (I'm not a hardware person either.)
 
Old 08-12-2003, 08:50 PM   #3
WanglessOlasov
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Hmm... i tried 'cdrecord -scanbus', both as a normal user and as root, but each time i got the same error:

# cdrecord -scanbus
Cdrecord 2.0 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jörg Schilling
cdrecord: No such file or directory. Cannot open '/dev/pg*'. Cannot open SCSI driver.
cdrecord: For possible targets try 'cdrecord -scanbus'. Make sure you are root.
cdrecord: For possible transport specifiers try 'cdrecord dev=help'.

Also, i've been using xcdroast, not cdrecord, but i guess xcdroast is just a front-end for cdrecord, isn't it? Oh, and something else i forgot to mention: raid controllers... i thought that they allow an array of drives, but beyond that (or even that far) i'm not sure.
 
Old 08-12-2003, 10:18 PM   #4
slakmagik
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/dev/pg*? Huh.

I should have really kept a notebook because I can never remember what I did. I think what I did is wrong, too. I can burn CDs, including ISOs but nothing I burn that's supposed to be bootable is. I posted a thread on it but never got any help. So something I did is wrong, but it was something like:

To lilo.conf add
append="hdd=ide-scsi"

To /etc/rc.d/rc.modules add
/sbin/modprobe ide-scsi
(I didn't have the line to uncomment, so added it.)

Then -scanbus gets me

root@slackath:~# cdrecord -scanbus
Cdrecord 2.0 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jörg Schilling
Linux sg driver version: 3.1.24
Using libscg version 'schily-0.7'
scsibus0:
0,0,0 0) 'CDWRITER' 'IDE5224 ' '001H' Removable CD-ROM
0,1,0 1) *
0,2,0 2) *
0,3,0 3) *
0,4,0 4) *
0,5,0 5) *
0,6,0 6) *
0,7,0 7) *

I can't remember what problems I was having that made the '/dev/hdd /mnt/cdrom' a pain or what told me it was actually /dev/sr0 but some research made me think I should make a directory, edit a symlink, and change /etc/fstab.

/dev/sr0 /mnt/cdrw auto noauto,users 0 0

Then, since the couple of front-ends I downloaded were more confusing to me than the command line, I just do, say

cdrecord -v speed=4 dev=0,0,0 ~/lab/woody-i386-1.iso

And I get a perfectly laid-out filesystem that doesn't boot. But, point is, the device is identified and burns.

Sounds like you've done all that, though. You could try

cat /proc/scsi/scsi

and see if that does anything. Maybe that would narrow it down to a device problem vs. a cdrecord-specific problem. Maybe the thing you are missing is the device file. Or, actually, you may not have scsi-emulation support in your kernel. Depends on what you booted with and installed. Beyond that, I'm really not sure. I don't see anything in cdrecord's manpage about /dev/pg*. Maybe 'ls /dev/pg*' and 'lsmod' to see if it's there and if the ide-scsi does indeed show.

And, yeah, all those apps are just front-ends on cdrecord.

As far as RAID, I have no idea.
 
Old 08-12-2003, 10:38 PM   #5
michaelk
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Ref material:
SCSI - Small Computer System Interface.
RAID - Redundant Array of Inexpensive Disks
ATAPI - AT Attachment Packet Interface, an extension to EIDE (also called ATA-2) that enables the interface to support CD-ROM players and tape drives.

The ATA or IDE interface supports 2 devices per controller. They are defined as master and slave. If you have only one device it is always the master. And of course the 2nd device is the slave. There are jumpers on the back of the drive to configure for either master or slave.

IDE RAIDS usually consist of two controllers where you can join 4 drives in various configurations such as mirroring, Spanning drives i.e all drives look like one.

SCSI RAID controllers can have up to 16 devices.

Yes, xcdroast is a just a frontend for cdrecord. I suspect that you do not have the proper modules being loaded.

You need
ide-scsi
sg
scsi_mod

Use /sbin/lsmod to see if they are loaded.

use modprobe to load

http://www.ata-atapi.com/
 
Old 08-12-2003, 10:49 PM   #6
WanglessOlasov
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Got it! turns out i had a line wrong in lilo.conf. Instead of append="hdc=ide-scsi", i only had append="hdc=scsi". (last time i listen to xcdroast's online faq... They said my kernel could support it, but obviosly it cannot. Maybe it's not their fault... i did sorta mess with mine a little). Now, everything seems to be working just dandy... xcdroast's automatic detections picks up on the scsi drives, cdrecord -scanbus shows everything correctly, and cat /proc/scsi/scsi shows the two devices.

uhh, one last question: when giving the device id's, i got numbers like [0,0,0] and [0,1,0] . What do those mean, exactly? are they sort of like the major and minor device numbers of block and character special devices? (wait, there are 3 numbers here... there goes my argument). I've tried searching the man pages for clues, but they really only tell you how to use them; the concepts themselves are lost.

Just curious, and thanks for all your help.... now i can actually burn cd's without my cpu maxing out...

P.S. If my fan keeps almost dying, and then i hit it to make it work again, does that make me as cool as "the fonz"? But seriously... i'm guessing i should probably replace it. Oh well. Thanks again.
 
Old 08-12-2003, 11:08 PM   #7
slakmagik
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Yeah, that's cool but if you crash your hard drive from the vibrations that wouldn't be so cool.

I'm not sure - it's not cdrecord specific - I think it *is* kind of like major and minor but for scsi? But I didn't find out - because I don't have a scsi dammit - and cdrecord is the only place the issue has come up so far.

Either way, glad you got it working. And maybe the hardware HOW-TOs at tldp will help you out with finding out more.
 
Old 08-12-2003, 11:12 PM   #8
michaelk
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The first digit is the bus controller id, second digit is the emulated SCSI ID and the third is maybe the LUN (multiple devices on the same ID like a jukebox).

Each BUS needs a unique number. I have two SCSI controllers so the are 0 and 1. If I connect my USB drive then I will have an additional bus 2. Since it also uses SCSI emulation aka usb mass storage

Depends on the SCSI controller but they can have up to 16 devices. Each device is assigned a number from 0 to 15. The controller usually being ID 7.
 
Old 08-13-2003, 04:35 PM   #9
WanglessOlasov
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From what i remember, the /dev/hd* devices are ide devices, and /dev/sd* are scsi... now that i'm using scsi emulation, do i have to specify a new device, for apps like cd players and mplayer, instead of hdc and hdd, which i previously used?
 
Old 08-13-2003, 11:20 PM   #10
michaelk
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You can use hdc and hdd for everything but cdwriting stuff.

FYI
/dev/sda, sdb ... are SCSI hard drives
/dev/scd0, scd1 ... are SCSI CDROM drives
/dev/sr0, sr1 ... also SCSI CDROMs
/dev/st0, st1 ... are SCSI tape drives

Hmm... can't remember what /dev a scanner is.
 
  


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