Multiple SCSI host adapters, naming of attached devices

Multiple SCSI host adapters, naming of attached devices

[Michael Pacey]

Sorry for posting this here, I'm sure you're all busy with 2.4.1 and 2.2.18
but I'm read the SCSI HOWTO and asked on #LinPeople to no avail:

Given two host adapters each with 1 disk of ID 0, how do I tell Linux which
is sda and which sdb?

After this I'll be filling the 2nd SCSI chain completely, so assigning a
different ID is not an option.

Thanks in advance.

--
Michael Pacey
michael@wd21.co.uk
ICQ: 105498469

wd21 ltd - world domination in the 21st century

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Re: Multiple SCSI host adapters, naming of attached devices

[Michael Pacey]

Of course I should have said this is linux kernel 2.2.17, an IBM PS/2 9585,
in-built 'IBM MCA' SCSI adapter and an AHA-1640 MCA card.

I now realise that in 2.4 I can use scsihosts=ibmmca:aha1542, but have no
info for 2.2.17.

Sorry for the lack of info previously :)

Thanks again.


On Tue, 30 Jan 2001 22:49:12 Michael Pacey wrote:
> Sorry for posting this here, I'm sure you're all busy with 2.4.1 and
> 2.2.18
> but I'm read the SCSI HOWTO and asked on #LinPeople to no avail:
> 
> Given two host adapters each with 1 disk of ID 0, how do I tell Linux
> which
> is sda and which sdb?
> 
> After this I'll be filling the 2nd SCSI chain completely, so assigning a
> different ID is not an option.
> 
> Thanks in advance.
> 
> --
> Michael Pacey
> michael@wd21.co.uk
> ICQ: 105498469
> 
> wd21 ltd - world domination in the 21st century
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> in
> the body of a message to majordomo@vger.kernel.org
> Please read the FAQ at http://www.tux.org/lkml/
> 
> 

--
Michael Pacey
michael@wd21.co.uk
ICQ: 105498469

wd21 ltd - world domination in the 21st century

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Re: Multiple SCSI host adapters, naming of attached devices

[Wolfgang Wegner]

Hi,
> Given two host adapters each with 1 disk of ID 0, how do I tell Linux which
> is sda and which sdb?
[...]
which leads me to the question:
Is there any reason for the (IMHO stupid) "dynamic" naming of
SCSI devices (in contrast to e.g. IDE devices or the "physical"
device naming used in Solaris)?
It may be possible always maintaining the "right" order with
one SCSI chain, but as soon as there is a second bus, it is
really a pain. Is devfs the only solution?

Regards,
Wolfgang

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Re: Multiple SCSI host adapters, naming of attached devices

[Andreas Dilger]

Michael Pacey writes:
> Given two host adapters each with 1 disk of ID 0, how do I tell Linux which
> is sda and which sdb?

You can't - you need to make sure either the cards are different and check
the SCSI host probe order, or the detection order in the PCI bus.  You
should only need to do this once, and simply use the order you get.

> After this I'll be filling the 2nd SCSI chain completely, so assigning a
> different ID is not an option.

If you are using ext2 filesystems, you don't care which is which, because
you can mount by filesystem UUID or LABEL, so just ignore the device names.
The same is true with LVM.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
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Re: Multiple SCSI host adapters, naming of attached devices

[Michael Pacey]

On Wed, 31 Jan 2001 01:05:51 Andreas Dilger wrote:

> If you are using ext2 filesystems, you don't care which is which, because
> you can mount by filesystem UUID or LABEL, so just ignore the device
> names.
> The same is true with LVM.
> 
> Cheers, Andreas


Well, I do care... This machine is confusing it's root filesystem with an
external SCSI disk.

But it looks like I can change the order in driver/scsi/hosts.c, though
this is not an elegant solution :(

Trying it now....

--
Michael Pacey
michael@wd21.co.uk
ICQ: 105498469

wd21 ltd - world domination in the 21st century

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Re: Multiple SCSI host adapters, naming of attached devices

[Michael Pacey]

On Wed, 31 Jan 2001 01:05:51 Andreas Dilger wrote:

> 
> If you are using ext2 filesystems, you don't care which is which, because
> you can mount by filesystem UUID or LABEL, so just ignore the device
> names.
> The same is true with LVM.

Well, I tried changing the order of driver loading in driver/scsi/hosts.c
after reading something on the web but that didn't work.

Then I tried what you (and another kind soul) suggested, i.e. mount by
label, and the machine fails to mount the / filesystem read-write on boot,
though I can do it manually. This is a Debian potato system. Well, I'm
tired and I've had too much wine and whisky so I am going to bed, but I
will attack this afresh tomorrow night...

Thanks for the advice, perhaps I'll need more tomorrow :)
 

--
Michael Pacey
michael@wd21.co.uk
ICQ: 105498469

wd21 ltd - world domination in the 21st century

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Re: Multiple SCSI host adapters, naming of attached devices

[Andreas Dilger]

Michael Pacey writes:
> But it looks like I can change the order in driver/scsi/hosts.c, though
> this is not an elegant solution :(

You can compile the "primary (rootfs)" adapter into the kernel, and load
the second adapter as a module.  This is supposed to work.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
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Re: Multiple SCSI host adapters, naming of attached devices

[Andrzej Krzysztofowicz]

"Michael Pacey wrote:"
> Of course I should have said this is linux kernel 2.2.17, an IBM PS/2 9585,
> in-built 'IBM MCA' SCSI adapter and an AHA-1640 MCA card.
> 
> I now realise that in 2.4 I can use scsihosts=ibmmca:aha1542, but have no
> info for 2.2.17.
> 
> Sorry for the lack of info previously :)

If the scsihosts= parameter helps you, you can look for a devfs patch for
2.2 kernels at
ftp://ftp.atnf.csiro.au/pub/people/rgooch/linux/kernel-patches/

--
=======================================================================
  Andrzej M. Krzysztofowicz               ankry@mif.pg.gda.pl
  phone (48)(58) 347 14 61
Faculty of Applied Phys. & Math.,   Technical University of Gdansk
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Re: Multiple SCSI host adapters, naming of attached devices

[Andrzej Krzysztofowicz]

"Wolfgang Wegner wrote:"
> > Given two host adapters each with 1 disk of ID 0, how do I tell Linux which
> > is sda and which sdb?
> [...]
> which leads me to the question:
> Is there any reason for the (IMHO stupid) "dynamic" naming of
> SCSI devices (in contrast to e.g. IDE devices or the "physical"
> device naming used in Solaris)?

Yes. Shortage of 16-bit major/minor numbers.

> It may be possible always maintaining the "right" order with
> one SCSI chain, but as soon as there is a second bus, it is
> really a pain. Is devfs the only solution?

You can try:
- loading scsi drivers as modules in appropriate order (possibly using
  initrd if root filesystem is located on any of them)
- using devfs names.

--
=======================================================================
  Andrzej M. Krzysztofowicz               ankry@mif.pg.gda.pl
  phone (48)(58) 347 14 61
Faculty of Applied Phys. & Math.,   Technical University of Gdansk
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Re: Multiple SCSI host adapters, naming of attached devices

[Michael Pacey]

Well, just so you know I am now building a 2.4.1 kernel for this machine so
I can use devfs.

So perhaps I'll try ReiserFS on this too... lots of fun :)

Thanks for everyone's kind words of wisdom.

--
Michael Pacey
michael@wd21.co.uk
ICQ: 105498469

wd21 ltd - world domination in the 21st century

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