Explaining Physical and Logical Device Names in Solaris 9
The /dev/dsk directory holds all the symbolic links to the actual device files in the  /devices directory for all of the hard drives the kernel 
sees on a system. The /dev/dsk files names are called "logical" because of their standard format and are easy to remember at the command line.

The logical path for an Ultra 5/10 primary hard drive (PCI/IDE):

# cd /dev/dsk
# ls
c0t0d0s0 c0t0d0s2 c0t0d0s4 c0t0d0s6
c0t0d0s1 c0t0d0s3 c0t0d0s5 c0t0d0s7
  • The "c0" represents the first instance of a host adapter on a system. Ultra 5/10's are pci architecture. Instance "c0" then represents the internal IDE controller. The internal IDE controller can have up to 4 devices on it.
  • The "t0" represents the target of the device. Since IDE can have up to 4 devices (t0-t3), t0 represents the first device on the controller.
  •  The "d0" represents the LUN (logical unit number) of the target. Internally this will always be set to zero. Internal drives only have one drive per target. The LUN number will be anything but zero if there is more than one disk per target (storage array).
  • The "s0" represents the slice or partition of the disk. Solaris supports 8 slices per physical drive. Slice 2 reports the size of the entire disk and should never be touched.
The kernel builds 8 device files per hard drive it finds attached to a system. Each device file accesses a slice on the hard drive. This is regardless
of whether or not the slices are being used. If a disk is only utilizing slices 0 and 3, the kernel will still build all device files 0-7. The CDROM is
 seen as a SCSI hard drive. The device files "c0t2d0s0"
through "c0t2d0s7" provide an interface to the access the CDROM.
The /devices holds all of the actual device files for all of the system components. Due to their conplex file names, symbolic links with more 
standard names for all device files in this directory are linked backed to the /dev directory. The following path is taken from an Ultra 5/10
primary hard drive (PCI/IDE):


o The "/devices" directory is the top level directory. All device files are located under this directory.

o The "pci@1f,0" represents the peripheral bus (PCI) for an Ultra 5-450 machines. The "pci" portion is the bus name. The "@1f,0" is the
slot address of the bus.

o The "pci@1,1" represents channel b of the PCI bus. Channel b on a PCI bus has 3 slots. The PCI bus has a channel a and b.

o The "ide@3" represents an IDE host adapter. This host adapter is slotted in slot 3. An IDE adapter can have up to 4 targets attached to it.

o The "dad@0,0:a" represents a ATA/IDE hard drive. The "@0,0:a" represents target 0 at LUN 0 slice 0 (a=0 b=1 c=2, etc.)
The kernel builds these device paths and files AUTOMATICALLY at a reconfiguration reboot. There should never be a need for a
system administrator
to add or remove these files.


By knowing the logical and physical device paths of devices, a systems administrator will be able to tell whether or not the kernel
can see a device by locating the
appropriate device files.

© 2004 Darren Hoch - darren at ufsdump.org