How does CAM determine the order to number drives ?

Pete French petefrench at ticketswitch.com
Sun Aug 1 07:09:26 PDT 2004


> You can wire down particular devices to a given SCSI bus, target and
> LUN.  Thus in your (4.x) kernel config you can say:
>
>     device scbus0 at ahc0
>     device da0 at scbus0 target 0 unit 0

Thanks for this - it looked as though it was just what I needed. I built
a kernel with scbus0 placed at ahc? (ahc0 would not compile - but I only
have one Adaptec controller in the machine). I would have thought this
was sufficient as it would then scan scbus0 first and thus find the 
Addapted conntected drive first. But it did not appear to do this - I
still had the ciss drives appearing first.

I assume for this that the second line is also necessary (which
surprises me), but at this point I had the lid of the machine
off so I simply moved cards around until the Adaptec was scanned
first by the kernel on startup. Which seemed simpler than putting
all the old controllers back and compiling yet another kernel :-)

But thanks for all the advice, (even if I didnt follow it to the letter
in the end). Very useful to know.

-pcf.

PS: For anyone interested in making a similar upgrade, the performance
    increase of the 5300 over the 4200 is very impressive. Around 65%
    on read performances from RAID-0+1 and 50% from RAID-5. Whether thats
    due to the change of BSD driver as well as the change of controller I
    don't know, but I am very happy with it!


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