Device File Definition

[David Hattok]

Could someone please tell me the correct range of numbers that can be used in each of the fields of a device file? Are there any numbers that are excluded from use?

Instance number of the interface card c0 to ??
SCSI target address t0 to 15?
Device number d0 to 7?

[Rita C Workman]

Well I hope this helps get you started.

First c# is the card instance (controller) for the ext_bus class of the interface card to which the disk is attached. The instance of a device adapter is unique for its specific class. Each separate physical disk controller will have a unique controller number
..the t# is the address of the device on the interface or target address. Typically the t# is the address set with jumpers or dip switches on the device itself. Each dis, on a SCSI, has its unique targer number.
..the d# is the device unit number (LUN) and can range from 0-7 (or 0-15 for fast wide SCSI). Note on single 7 to 0 with 7 (highest priority) reserved for the adapter itself and 14 to 8 (lowest priority).

An example:
/dev/dsk/c0t6d0 - block special file for disk 6 at controller 0.
/dev/dsk/c2t6d1 - block special file for LUN 1 on target (disk) 6 on the 3rd disk controller. Remember 0 can account for the first controller.

/rcw

[Bill McNAMARA_1]

The ioscan addressing points to a particular slot that your adaptor cards are physically located in.
The c comes from the instance no in the ioscan -fnk and identifies in which order the cards were detected by the installed kernel.
c numbers newer change unless you reinstall.
Usually they are in numeric order... but in either case unless Fibre Channel complicates things they identify a controller card.

The t is scsi id or fibre channel hex converted target. It identifies an element connected to the controller bus. Remember the controller is an element also and usually with the busses highest priority of 7 for scsi.

The d is disk/device and can either be a lun, 0-7 but for an individual disk will always be 0. When a lun or harware raid configuration is seen behind an addressable controller, the lun number identifies the d in the device file.

best way to interpret the addressing is to print out an ioscan:
ioscan -fnk |lp -onb -o12 -olandscape

walk behind your server and draw cableing out.
The match the ioscan output to the devices.

Later,
Bill