SATA & SCSI Conflict?

rlinuxr · 03-22-2006, 05:54 PM

I have a Dell Dimension Desktop with SATA hard disk.
I installed Red Hat 3.0 (Update 6).
The kernel names the local hard disk as /dev/sda, which I understand is how Linux handles SATA.

Then, I installed Adaptec PCI SCSI card and attached an external SCSI hard disk. The problem is that after the machine is rebooted, Linux does not show this device as /dev/sdb (or sdc etc) as I would expect.

If during restart, I press CTRL+A to get into Adaptec SCSI utilities, I see that the external disk is there and I can even format it. The machine BIOS also shows the external SCSI disk under "Boot Device Order" information.

What could be wrong here?

Interesting thing is that if I do the same on another Dell box with P(ATA) local instead of SATA, and using the same Adaptec PCI card, the external SCSI disk gets picked up as /dev/sda. The PATA disk in this case is /dev/hdb as you would expect for an IDE device.

I would appreciate any help with this issue.

Thanks,
Ravi.

Brian1 · 03-22-2006, 07:40 PM

Does the command as root show anything ' fdisk -l '?

rlinuxr · 03-22-2006, 08:00 PM

Hi Brian,

The 'fdisk -l' command only shows the local SATA drive as /dev/sda.

Thanks,
Ravi.

rlinuxr · 03-23-2006, 10:09 AM

Can anyone please help?

Emerson · 03-23-2006, 10:11 AM

Uh, my wild guess is the kernel has no built-in support for your SCSI controller and module (if exists) is not loaded. Try loading it manually.

rlinuxr · 03-23-2006, 12:34 PM

Thanks, Emerson.

I have the same exact kernel installed (in the same exact way) on the other box which has PATA drive instead of SATA and it works.

Emerson · 03-23-2006, 04:23 PM

Could you run lsmod on both machines to see which SCSI modules are loaded?

rlinuxr · 03-23-2006, 09:03 PM

From the box that works fine:

# lsmod | grep -i scsi
scsi_mod 106924 3 [sg aic7xxx sd_mod]

From the box that does not work:

# lsmod | grep -i scsi
ide-scsi 12496 0
scsi_dump_register 2368 0 [ata_piix]
scsi_mod 115756 4 [sg ide-scsi ata_piix libata sd_mod]

Thanks.

Emerson · 03-24-2006, 04:59 AM

aic7xx is not loaded. What happens if you try to load it with modprobe?

rlinuxr · 03-24-2006, 09:03 AM

Emerson, thanks for helping out. Appreciate it

# locate aic7xxx
/lib/modules/2.4.21-37.EL/kernel/drivers/scsi/aic7xxx
/lib/modules/2.4.21-37.EL/kernel/drivers/scsi/aic7xxx/aic79xx.o
/lib/modules/2.4.21-37.EL/kernel/drivers/scsi/aic7xxx/aic7xxx.o
/lib/modules/2.4.21-37.EL/kernel/drivers/scsi/aic7xxx_old.o
/lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx
/lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx/aic79xx.o
/lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx/aic7xxx.o
/lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx_old.o

# uname -a
Linux mastaba2 2.4.21-37.ELsmp #1 SMP Wed Sep 7 13:28:55 EDT 2005 i686 i686 i386 GNU/Linux

# modprobe -a /lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx/aic7xxx.o
modprobe: Can't locate module /lib/modules/2.4.21-37.ELsmp/kernel/drivers/scsi/aic7xxx/aic7xxx.o

# cat /etc/modules.conf
alias eth0 tg3
alias scsi_hostadapter ata_piix
alias sound-slot-0 i810_audio
post-install sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -L >/dev/null 2>&1 || :
pre-remove sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -S >/dev/null 2>&1 || :
alias usb-controller usb-uhci
alias usb-controller1 ehci-hcd
alias scsi_hostadapter1 aic7xxx

Emerson · 03-24-2006, 09:36 AM

-a option is used only when you need to load multiple modules at once. Full path is also not needed. Try just plain modprobe aic7xxx. If it fails check dmesg.

rlinuxr · 03-24-2006, 10:02 AM

Ok, that worked.

Now I can see the external scsi drive as /dev/sdb.

Not sure why it is not getting automatically loaded at boot time? Maybe I will put the modprobe command in one of the rc init files.

In any case, thanks a lot for your help. Truly appreciated.

Regards,
Ravi.

Emerson · 03-24-2006, 10:22 AM

Glad to hear it

I'm sure there is an appropriate place where modules autoload from, for instance it is /etc/modules.autoload.d/<kernelversion> for Gentoo. Just find out how RH does it.

rlinuxr · 03-24-2006, 01:11 PM

Ok. Resolved the boot time issue as well.

On RedHat, the modules to be autoloaded at boot time are specified in /etc/modules.conf file.

My original /etc/modules.conf file had the following entries:

alias eth0 tg3
alias scsi_hostadapter ata_piix
alias sound-slot-0 i810_audio
post-install sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -L >/dev/null 2>&1 || :
pre-remove sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -S >/dev/null 2>&1 || :
alias usb-controller usb-uhci
alias usb-controller1 ehci-hcd
alias scsi_hostadapter1 aic7xxx

Here, the aic7xx is listed last and the scsi adapter for local PATA drive (ata_piix) is listed almost at the top. I changed the entries as follows:

alias eth0 tg3
alias scsi_hostadapter1 aic7xxx
alias scsi_hostadapter ata_piix
alias sound-slot-0 i810_audio
post-install sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -L >/dev/null 2>&1 || :
pre-remove sound-slot-0 /bin/aumix-minimal -f /etc/.aumixrc -S >/dev/null 2>&1 || :
alias usb-controller usb-uhci
alias usb-controller1 ehci-hcd

Basically, I listed aic_7xxx scsi adapter before the ata_piix one. After that I ran the following commands:

cp /boot/initrd-2.4.21-37.Elsmp.img initrd-2.4.21-37.Elsmp.img.bak
mkinitrd -v -f /boot/initrd-2.4.21-37.ELsmp

Rebooted the box, and bingo external scsi drive is immediately visible after reboot without having to do manual 'modprobe aic_7xxx' command.

Emerson -- thanks, once again.

Regards,
Ravi.