Here, in rough order of frequency, are the most common problems and some things you can do to solve them:
If you experience numerous read/write errors, noticeably slower performance, excessive initialization time, or tapes that eject themselves immediately after they are inserted, first suspect a dirty drive. Cleaning the drive as described in the preceding section usually cures such problems immediately. Retensioning tapes periodically also helps avoid this problem.
Configuration problems or incompatibilities with backup software or drivers
If the backup software doesn't recognize the drive, can't load the driver, or does not contain a driver for the drive, first make sure that the host adapter recognizes the drive as present at boot time. For SCSI, ensure the operating system recognizes the SCSI host adapter and download and install later drivers from the host adapter manufacturer's web site, if any are available. If you have recently installed a new version of your backup software, verify that it contains support for the tape drive, and download updated drivers for that drive if necessary. If your tape drive manufacturer provides downloadable firmware updates, download and install the latest recommended firmware for your drive.
SCSI communication problems
If the controller does not recognize the tape drive or the controller or system hangs at boot, the most likely cause is physical damage to or a configuration problem with the SCSI chain. First verify that the data and power cables are undamaged and fully connected to the drive. Verify that there are no SCSI ID conflicts and check termination, particularly if you have just added a new SCSI device to the chain. If everything appears correct and the problem persists, use the SCSI BIOS utility to make one or more of the following changes to the host adapter configuration: disable Sync Negotiation; disable Wide Negotiation; set the transfer rate to the lowest available value; enable Disconnect. In other words, slow things down until the drive functions properly. If none of this works, the most likely problem is a malfunctioning drive or controller. If other devices on that chain function properly, suspect the drive.
SCSI bus scan displays drive on all or most SCSI IDs
This is nearly always the result of assigning the tape drive the same SCSI ID as the host adapter. Reassigning the tape drive to an unused SCSI ID fixes the problem.