ATAPI tape drives are physically installed and configured just like any other ATAPI/IDE device: set the drive's Master/Slave jumper; secure the drive in an available drive bay using four screws; connect the data cable, aligning Pin 1 on the drive connector with the colored stripe on the cable; and connect the power cable. Note the following issues when installing an ATAPI tape drive:

• 1. Installing a tape drive on the same IDE channel as a hard disk risks data corruption. If the system has one hard disk, install it as the Primary Master and the tape drive on the Secondary channel. If the system has two hard disks, install both on the Primary channel, and install the tape drive on the Secondary channel. Do not install three ATA hard disks in a system with an ATAPI tape drive. If the system has an ATAPI CD-ROM drive, make that drive Secondary Master and the tape drive Secondary Slave. If the system has no ATAPI CD-ROM drive, make the tape drive Secondary Master.

• 2. Some tape drives have configuration jumpers to enable such things as hardware compression, read-while-write, DMA/PIO mode, and emulation mode. If your drive has one or more of these jumpers, set them as follows:

  Hardware compression

  Ordinarily, enable this option to allow the drive itself to compress the data stream before recording it to tape, but note that software compression is sometimes more efficient than hardware compression. If you enable hardware compression, disable compression in your backup utility. Leaving both enabled results in "churning" that can actually increase the size of the data being written to tape. Some backup utilities have a configuration checkbox that allows you to select hardware compression. We've never been entirely sure of the purpose of this checkbox because hardware compression is (or should be) transparent to the backup application, but if your backup utility has such a checkbox, it's probably a good idea to mark it if you enable hardware compression on the drive.

  Although different drive models from a particular manufacturer may supposedly use compatible hardware compression, any tape made with hardware compression enabled may be unreadable except in the drive that wrote it. There is no guarantee that you will be able to read a hardware-compressed tape made on one drive with any other drive. Something as subtle as a minor difference in firmware revision may prevent reading a compressed tape even in a seemingly identical drive.

  Read-while-write

  If your drive has a jumper to enable read-while-write, doing so allows the drive to use its separate read head to read and verify data immediately after it is written, avoiding the need for a time-consuming second compare pass. Not all backup software supports this function. If your backup software does support it, you may need to enable support for it within the backup program.

  DMA/PIO mode

  DMA mode increases throughput and reduces CPU utilization, but not all tape drives can operate in DMA mode. If your drive is DMA-capable, it may have a jumper to configure the drive for DMA mode versus PIO mode. In general, if the tape drive is the only device on the ATA channel, or if the other device on that channel is also DMA-capable, enable DMA mode for the tape drive and enable DMA support for that channel in the operating system. If the tape drive shares the channel with a PIO-only device (e.g., an older CD-ROM drive), disable DMA mode for the tape drive or (better) replace the other device with a DMA-capable device.

  Emulation mode

  Some tape drives can emulate other drives via a jumper setting that causes the drive to return incorrect identification data to the operating system. For example, we have an old Tecmar Travan NS20 tape drive that was jumpered by default to identify itself as a Wangtek Model 51000. Removing this jumper causes the drive to identify itself as a Tecmar Travan NS20. Using emulation allows a new drive model to be used with older software that does not support the new model. Set this jumper, if present, according to the manufacturer's instructions.

• 3. Recent BIOSes allow setting boot sequence to first attempt booting from a CD-ROM drive. What this actually tells the system is to boot from the first ATAPI device. If an ATAPI tape drive is configured as Master (even on the Secondary channel), a system so configured may attempt to boot from the tape drive, which causes the system to hang. You can avoid this problem by setting the CD-ROM drive to Secondary Master and the tape drive to Secondary Slave. This problem may also occur if the tape drive is the only device on the Secondary channel, whether it is configured as Master or Slave. If you cannot correct the configuration or disable CD-ROM boot in BIOS, boot the system with no tape in the drive.