SCSI Termination

[bigbeark]

Any SCSI experts here? I am using an ASUS CUR-DLS with onboard LSI SCSI and Ubuntu Linux. I was using a Seagate Cheetah ST##^&52LC Drive until it got too hot. I am now using an IBM drive whih I am pretty sure is a quantum/maxtor - cool running but not as quiet as the Seagate. Ubuntu Logs shows:

6.518136] scsi target3:0:0: FAST-80 WIDE SCSI 160.0 MB/s DT (12.5 ns, offset 62)
Apr 18 15:05:31 barry-desktop kernel: [ 6.523632] scsi target3:0:0: Ending Domain Validation

I use a SCA adapter which has a small resistor on it and two pins marked TRM PWR . I am not using a jumper on these pins.

The Seagate site has the following info regarding their SCSI drives:

Configure Termination
Only the devices at each physical end of a SCSI bus need to be terminated. The SCSI host adapter normally will provide termination for the controller end, therefore only terminate the last drive on the end of the cable. LVD drives do not have any provision for onboard termination; therefore, termination for LVD drives must come from another device or from an external terminator. Use only active SE or LVD terminators.

Configure Terminator Power
Active terminators must receive power from some source. The default configuration results in the drive not supplying termination power to the bus. Usually, the host adapter provides term power. Check the user's manual for your host adapter. Drive models ending in LC cannot be configured to provide termination power to the bus.

My current configuration works fine, but I am not sure if I am operating in SE or LVD mode, and if I am getting optimal performance, since I am not using "active Termination"
unless that is being supplied by the onboard SCSI adapter.

Can anyone here clarify this for me?

[shadow]

Re: SCSI Termination

For the SCSI standard. Both ends of the cable have to be terminated.

I have only used passive terminators..they have worked well for me. I am not sure when active terminators would become truly useful.

Now one end of the cable is normally terminated internally by the SCSI adapter. Usually this is turned on by default. The other end of the cable also needs to be terminated. Usually by clipping on a passive terminator onto the end of the cable (all the cables I had already had them installed).



I think that some SCSI devices may have a jumper which can activate a terminator. However I am not exactly sure and it will depend upon the device. I have always used a passive terminator to terminate one end of the SCSI cable while relying on the SCSI adapter to terminate the other end.

[japlytic]

Re: SCSI Termination

If you have internal or external devices, turn on the termination on the host adaptor.
If you have both internal and external devices, turn off the termination on the host adaptor.
Active terminators of the correct type (SE or LVD) are strongly recommended. FPT terminators are recommended for high noise environments.
For the type of SCSI interface (SE or LVD), consult the datasheet of the device.
On some LVD devices and host adaptors, they will default to SE mode when any SE device (including terminators) or host adaptor is connected.
HVD devices and host adaptors are rare these days, and must only be connected to HVD devices and host adaptors.