[Techtalk] PCI, IRQ, and Raid

[Malcolm Tredinnick]

On Mon, Sep 23, 2002 at 02:45:16AM -0400, Andrew wrote:
> 	A few weeks ago I was triing to put together a 4 dr raid. I was not 
> sucessful. I was annoyed, I could at that time ask the "right" 
> questions. So I went and studied the matter. I am putting together a 
> list of what is actually in the box and what the software thinks is there.
> 	
> 	As root in a terminal window, in "/proc/", while attempting to copy the 
> content of the file "PCI"... I could read it or "view" it using 
> MidnightCommander, BUT was unable to copy it. It would open as a blank 
> page in a text-editor(gedit).It would open as a blank page when I 
> selected edit in MC. Again as 'view" it would show a list (totally 
> wrong) of PCI devices.In edit or copy it shows blank/empty/file.

Ooh, ooh ... pick me! This drove me mad when I started using Linux (a
long time ago, now, but it was traumatic at the time). :-)

The /proc hierarchy is a virtual filesystem that is actually stored in
RAM. The things in it look like files, but they are not files. Notice,
for example, that they all appear to have length 0 when you do 'ls -l',
but you can run 'cat /proc/uptime' and something is in there. Note,
also, that 'less /proc/uptime' does not work -- this is because 'less'
reads the length before beginning (so that it knows when to stop) and
the length of a /proc file is 0.

To copy the contents of a /proc file into another file, you need to do
something like

	cat /proc/foo > other.file

I am a bit confused about how this is all relevant to installating a
four drive RAID setup, but I am guessing you have stepped back a bit and
adopted a more holistic approach.

> 	Do I need to look someplace else?  Where? Whay can't it (/proc/pci/) be 
> copied?
> 
> This (making a list)seems to me the first step in fixing the machine.
> The bus (including AGP) is reading only two of the six slots correctly
> empty slots show non-existant 10-100 cards. The AMI bios looks to be
> reading it correctly.

Are you saying that it is reporting more devices than you think you
have? Be careful -- PCI is a tricky creature. On board devices will also
show up, even though they don't occupy slots; so make sure you account
for on-board sound chips, network chips and even USB ports.

I don't think I have heard of a case of /proc/pci getting things wildly
wrong, but that could be because I am leading a sheltered life or
something (Jeff Dike or somebody will now pop up and point out that it
is as common as dirt). :-)

> In the next few days I should get the newest CD 8.0 to 8.2 Mandrake.
> Is it likely the new software will fix this??

Just by the way, as somebody pointed out here recently, Mandrake 9.0 is
going to be out _very_ shortly. So if you are paying money for the CDs,
you may wish to wait a month (if you can afford to).

Cheers,
Malcolm