[nSLUG] Suggestions for Distro

Daniel Morrison draker at gmail.com
Sun May 31 12:57:00 ADT 2009


2009/5/31 J. Paul Bissonnette <jpaulb at eastlink.ca>:
>> You are making big generalizations. How does the BIOS "order" ATA,
>> SATA, and SCSI? I have never seen one that does this -- unless you
>> mean "BIOS boot order", which is really something different. In what
>> way is choosing a disk to boot a pain?
> "BIOS boot order"
> The BIOS on the MSI K8N Neo9 has a boot order
> IDE Primary Master, Slave
> IDE Secondary Master, Slave
> Third Master
> Fourth Master
> Fifth Master
> Sixth Master

This may be the way the BIOS "discovers" or enumerates them, but "boot
order" is generally something different (e.g. CDROM, Floppy, HDD; or
SCSI, HDD, CDROM, etc...)

> The SCSI drives are appended to the end of that list

Typically because the SCSI BIOS is separate from the main BIOS, so the
main BIOS skips to the SCSI initialization after the POST is complete.
However you can still configure the BIOS to boot the SCSI disks first
if you want.

> I am comparing Ubuntu 9.04 or 8.04 & Debian Squeeze
> Ubuntu installation, at the partitioner stage, identifies the SCSI
> drives as sda, ... sdn
> The SATA drives sdn+1... and then the ATA are at the end of the list
>
> Debian has always identified the drives in the same order as the BIOS does.
> Primary master is hda
> Primary slave is hdb, etc.
> First SATA is sda.. etc
> Then the SCSI drive

Well, I'm by no means an expert, but I think the hdX devices are
obsolete. My distro, Slackware, "has always" had /dev/hdX devices
also, but... not anymore. I think you're confusing the comparison
between "old way & new way" with a comparison of "Debian & Ubuntu".

Now that libata is handling everything, the order seems (to me) to be
based on seniority: "real" scsi devices first, modern SATA devices
next, and legacy devices last.

True enough, Debian is conservative and upgrades slowly, while Ubuntu
tends to be on the bleeding edge. Guessing that the final change
occurred approximately in kernel 2.6.21, I find that Debian 4.0 "etch"
and all earlier releases would have done things the old way, and
Debian 5.0 "lenny" is doing things the new way. Ubuntu would have
switched over between 7.04 (Feisty Fawn) and 7.10 (Gutsy Gibbon).

> With Ubuntu the first bootable disk is sda which could be either SCSI,
> SATA or ATA, depending on what types of hdds are installed.
> I asked in the Ubuntu forum when this first became apparent with 8.04. I
> had just upgraded from 7.10; where there was no issue. Never got a reply
> to the question.

Perhaps my estimates are slightly off... 7.10 used kernel 2.6.22. 8.04
used kernel 2.6.24.

...no, I think I'm right, and you're off.  I found this text on a forum:

>> I read this on the Ubuntu-devel-discuss mailling list...
>>
>> "Starting from Gutsy, the old IDE chipset drivers are no longer included
>> in the kernel package. The libata based drivers, being cleaner and
>> easier to maintain, have taken the places of the old drivers.

I understand that it may be confusing to see a list of similar
"/dev/sdX" devices. You can always "cat /proc/scsi/scsi" to get lots
of detail about each device (enumerating host adapters for each
device, and listing the device model numbers). Or with "hdparm -i
/dev/sd?" you can even read the serial numbers.

> My solution was to remove the SCSI and the SATA install
> the system and manually install the SATA. The SCSI hdd has been retired
> since Ubuntu 8.04.

Well, I'm sorry, but removing hardware is a drastic solution.
Effective, surely, and if it's easy for you, then fine, but don't
complain about it then. Without touching the hardware, using LILO, I
would simply edit /etc/lilo.conf, change the line "boot = /dev/sda" to
point at a different device, and re-run /sbin/lilo. Using grub... well
there is some arcane but straightforward syntax...something like:
# grub
device (hd0) /dev/sdb
root (hd0,0) # <--- assuming your boot filesystem is on partition
"zero" (i.e. one)
setup (hd0)

> Debian is not using the UUID system, there is no problem mixing drives,
> Ubuntu is using it; there is a problem mixing drives.

I have guessed that your problem is confusion about which disk is
which -- other than that, you haven't explained what the problem
really is.

>  From my experience with Ubuntu; when I added 1 SATA to the ATA drives;
> I would have to upgrade all the drives to SATA to get it to work
> properly.

What do you mean "properly"?

> It maybe a Motherboard issue also.

I think you must be correct. I certainly have no issues running SATA
and legacy PATA drives at the same time; my only problem is that my
SATA-based motherboard has only one PATA controller, so after my
optical disk, I have only one PATA connector left.

Of course, anytime you change the hardware, problems may result -- you
might have to change all the /dev/sd? entries in your /etc/fstab. This
is why distros use UUIDs in the /etc/fstab, to avoid this problem.

> Debian text based installation was finished in a jiffy, no fuss.
> I just do not have the time, energy, experience or the interest to spend
> hours trouble shooting glitches introduced between one upgrade and another.

Well, I'm getting to be a bit sorry I jumped in on this discussion,
because I'm not finding it to be very productive. I won't deny that
the change to libata was likely made abruptly, without much warning,
and so caused some glitches and difficulties with some people's
hardware. But there's no denying that it's better: faster, more
stable, more versatile. You have to live with these things if you want
progress. By all means stick with what works for you, if you cannot
manage the changes in version upgrades. I'm afraid though, on this
matter, that the change will be forced upon you (much like GTK2!)
eventually.

If you want to upgrade to Debian Lenny, you will find the same
problems. I found a discussion of how to disable libata (and rely on
the old IDE drivers) for Lenny here:

http://forums.debian.net/viewtopic.php?p=173905

I hope it may be useful.

-D.



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