[SLL] /dev/sd names not in motherboard order

[Brian Lane]

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On 3/2/09 11:34 AM, Derek Simkowiak wrote:

>     I would really like to understand how the device names (/dev/sda, 
> etc.) are discovered and assigned by Linux.  When one of the drives in 
> my 6-disk RAID box fails, I'll need to sit there, unplugging drives one 
> by one from the motherboard to see which drive corresponds to the broken 
> one.  (That's the one major disadvantage of Linux software RAID that 
> I've found... hardware RAID gives you nifty blinkenlights on 
> hot-swappable drives.)

Actually, I think I have the answer for that. Maybe. From my noes when I
bult my 4 drive software RAID:

The SATA driver creates a separate bus for each SATA connector. The
/dev/sdX device is then associated with a bus. This is listed in dmesg,
but should be available somewhere else as well...

Ok, /sys/block/sdX/device is a symlink to the scsi host bus that it is
attached to. So, I just need to associate those busses with the drawers.
1 	3:0:0:0
2 	1:0:0:0
3 	0:0:0:0
4 	2:0:0:0

sda, sdb, sdc, sdd all get assigned based on which drives are active.
You need to look at /sys/block/sdX/device to determine which drive is
actually in need of replacement.

Brian


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