How many drives?

[Nigel Henry]

On Thursday 27 September 2007 17:24, Andy Green wrote:
> Somebody in the thread at some point said:
> >    What's a quick (even dirty) way of finding out how many HDs a system
> > has?  Assuming that:
> >
> >       a) Not all of them are actively used, so they wouldn't be in
> >          /etc/fstab (or visible in df)
> >
> >       b) /var/log/dmesg isn't available for scanning
> >
> >       c) /var/log/messages isn't available for scanning
> >
> >       d) And access to the boxes is (somewhat) restricted - they're in
> > racks, and I really don't feel like yanking each and every one)
>
> Cool thing...
>
> $ cat/proc/diskstats
>
> lists unmounted stuff as well while the drive is still physically present.
>
> -Andy

I had a look at /sys/block on one of my machines, but it's a bit vague as 
there are 3 harddrives on the machine, plus 3 optical drives.

By contrast, cat /proc/diskstats is much more informative. It lists the 
harddrives first, then further down the list, the optical drives.

A question:

At the start of each line is a number.

Memory is "1"
The 2 harddrives on ide0 are "3"
The harddrive on the pci ide adaptor card is "33"
The 2 optical drives on ide1 are "22"
The optical drive on the pci ide adaptor card is "34"
md0 is "9"
And fd0 is "2"

Is there someplace where this numbering system is explained?

Nigel.

btw: What's md0?