SCSI Option Bit

SCSI Option Bit Setting

Use the following procedure to determine the SCSI option bit setting under Solaris 2.x:

# adb -k /kernel/unix /dev/mem (Solaris 2.0 - 2.4)

# adb -k /dev/ksyms /dev/mem (Solaris 2.5)

scsi_options/X

$q

SCSI Option Bits

Disconnect/Reconnect	0x008
Linked Commands	0x010
Synchronous Transfer	0x020
Parity	0x040
Tagged Queuing	0x080
Fast SCSI	0x100
Wide SCSI	0x200
Fast 20	0x400

Tagged Queuing

Tagged Queuing allows a disk to receive more than one command at a time and to perform the commands in an order that reduces disk latency in many applications. Tagged Queuing is implemented in Solaris 2.1.

Some SCSI disk drives may not properly implement Tagged Queuing. Disable Tagged Queuing in the driver to prevent unrecoverable failures. Add the following to the /etc/system file under Solaris 2.x:

set scsi_options=0x178

Wide SCSI

To enable Wide SCSI under Solaris 2.3, add the following to the /etc/system file:

set scsi_options=0x3f8