How do SCSI map to /dev/sd*?

humbletech99 · 12-16-2005, 05:04 AM

does anybody know how SCSI devices on the channels map to the sda sdb etc devices?

I can cat /proc/scsi/scsi to see the devices on the channels and their id and manufacturer but this doens't tell me which one is which block device under /dev.

arckane · 12-16-2005, 06:55 AM

I would imagine (but don't quote me on this) that the SCSI LUN will map to the sd*. Example:

SCSI LUN 1 == sda
SCSI LUN 4 == sdb
SCSI LUN 9 == sdc

I'd break out the google-monkey for confirmation, but I believe this is how it's done. The SCSI LUN is the Logical Unique Number assigned to each drive, usually with a jumper. Number 7 tends to be the physical card/controller.

humbletech99 · 12-16-2005, 07:12 AM

no because all the drive are LUN 0 in this machine which has nearly 20 SCSI disks

michaelk · 12-16-2005, 07:21 AM

Typically, the first recognized drive (lowest SCSI id) on the first recognized controller will be sda, next sdb and so on.

humbletech99 · 12-16-2005, 07:33 AM

is there any command to see the kernel's table of mappings?

this would be much easier and faster as well as knowing that you haven't made a simple mistake...