Messages in this thread | | | Date | Tue, 12 Oct 1999 00:50:17 +0100 (IST) | From | Paul Jakma <> | Subject | Re: scsi disk detection and /dev names, RE: My $.02 on the raging de vfs debate |
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On 11 Oct 1999, H. Peter Anvin wrote:
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.
in that case we should consider not including PCI location. ie let controllers continue to be autodetected, but describe devices/functions of them according to location. I think this would suit scsi and busses quite well.
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.
true. though i think in the case of scsi 90+% of the time the change is a disk swapped or added (eg hardware failure or pressing need for expansion). Re-arranging busses / controllers might imply a planned rebuild.
In the former case there's a good chance admin is stressed, :), so unambigous device names would be nice, to avoid confusion.
In the second case you know the hardware well enough, and just need to watch the boot messages to watch for controller detection. Then you'll know "this device has to be /dev/controllerXdeviceYfunctionZ".
You don't have to remember the order of detection of individual devices - which you would with what we have now. And new hardware config is when you have least familiarity with detection order, but most with physical location.
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.
So we'll just have to show more imagination than Sun! :) The solaris PCI based names are a bit cumbersome, i agree.
-hpa
regards, -- Paul Jakma paul@clubi.ie PGP5 key: http://www.clubi.ie/jakma/publickey.txt ------------------------------------------- Fortune: The only difference between a car salesman and a computer salesman is that the car salesman knows he's lying.
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