The ARCserve Tape Engine sends SCSI commands to the SCSI Port provided by the driver for the SCSI or Fibre controller via an API in the OS. When the OS fails to received a response back it will send a NT SCSI Port Error back to the Tape Engine.
Lets examine a Write command as an example. 1) Job wants to write data to tape. 2) Data is placed into the Tape Engine buffer. 3) Buffer fills so Tape Engine issues a Write command containing the data. 4) Command is sent to the OS API, 5) OS API passes the command to the SCSI Port provided by the controller driver. 6) Controller driver sends command to the controller and through the correct bus to the device. 7a) Command passes from the controller to the cable, 7b) If this is Fibre it will then go to the switch and possible a Fibre to SCSI bridge, 8) Command is received by the tape drive it is addressed to. 9) In the case of SCSI the command will travel the full length of the buss until it is absorbed by the terminator. 10) The tape drive will send the data to itÆs internal buffer. 11) The data will be written to tape from the buffer.
Now if anything happens along the way to cause this command to be lost or corrupted the OS may not get a response back and the result will be and NT SCSI Port error. Here are some common problems.
At the OS level a conflicting application, such as an OS tape and/or media changer driver. It could also be an application designed to control an optical or CD library. At the controller level it could also be a driver problem, such as a bug or the need for an OEM specific version of the driver. At the controller level it could also be a setting such as enable wide negotiation, or the DMA transfer speed. At the cable level for SCSI it might not be properly shielded or made to meet the specific resistance range. Also for SCSI the termination might not be set correctly, it might be the wrong type of terminator or defective. If a Fibre to SCSI Bridge is used, then these things need to be followed at the SCSI side of the bridge. For Fibre it could be cable, GBIC, switch and bridge firmware/setting. Hardware or software configuration for the tape drive within a library could cause problems with any or just a specific drive. Finally a firmware or hardware problem within the tape drive could result in the error.
A problem with any of this could result in exactly the same NT SCSI Port error. Thus we find that from the error it is not possible to tell were the problem is.