> This is correct; the program "scsidev" by Eric Youngdale has done this
> for a long time, for example.
>
> A few more things to remember when you're talking about
> "location-based names":
>
> 1. PCI bus numbers are fairly volatile; they are assigned sequentially
> by a depth-first search. Inserting a multiport Ethernet card
> (which usually have PCI-PCI bridges onboard) could move a whole lot
> of bus numbers for you. Same thing with SCSI controller numbers.
Yes, but in my experiance, you're much less likely to have a
controller die on you than a disk. If you move a controller you realize
that things may change. You also tend to do things like change controllers
during scheduled down-time. The same is no where near true regarding
disks. Much of the problem being, if a disk dies, you have to spend time
figuring out what disk died when you reboot, you can't just say 'oh, disk
c0t3d0s0 died, well, that is target 3 on the chain..'... You tend to have
to mount all of this disks, then hope you can remember what was supposted
to be on what disk.
> 2. Consider if location-basis is really what you want, and if so, if
> it really matters. Rearranging your SCSI busses, for example, is
> probably quite common. On busses where you have device serial
> numbers, or for disks where you have labels, it probably would
> provide a better basis.
I hear talk about this, and it seems like a cute thought, but for
some reason it just doesn't sit very well with me. Serial numbers may be
okay, but again, if the drive dies, chances are I'm not going to remember
the serial number, whereby I can look at a stack of disks (That are in
order, as I tend to keep them) and go 'okay, disk 3 died, third disk in
the stack...'. Also, if you're mounting by label, and you have a couple
of disks in a raid configuration, figuring out which one died could be
harder than it should be.
I suppose you could label the front of each disk (Assumeing external
disks, which is what I deal w/ alot) with the label you give it, but those
labels seemed rather long... Also, with multiple partitions each having it's
own label, you could have 4 or 5 labels per disk to check...
> 3. Solaris seems to teach the lesson that if you make the device names
> too complex, noone will use them. Solaris has a very complete
> location-based device naming scheme, but I know very few Solaris
> administrators who use those names, as opposed to the short
> symlinks.
Except that under Solaris, the symlinks are location-based
themselves, just... aggregated a little bit. :)
Stephen
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