Several companies such as Seagate and Western Digital manufacture external hard drives that can be connected to a computer via a 1394/FireWire or USB 2.0 connector. They can also be used as an adjunct to existing system drives, a mass backup device or as a way of copying massive amounts of data to other PCs.
Many problems have been reported with external hard drives, ranging from data corruption to total system freeze-ups when copying large amounts of data. There is no one reason for these problems, but rather a galaxy of possibilities that need to be examined systematically.
Problems with the host controller. Host controllers come with a variety of chipsets. For example, the most common chipset with Firewire controllers is the Texas Instruments chipset, but Lucent also makes a 1394 controller chipset as well. If one is not working correctly, it may help to switch to another manufacturer, or a more recent model of the same unit (if the earlier chipset implementation was buggy).
Firmware problems. External drives use an IDE-to-1394/USB bridge controller, usually made by one of several manufacturers. Oxford is the most popular, but another common variety is made by a Taiwanese company named Prolific. The chipset may have undergone revisions since the time the unit was manufactured, and there may be an update to the unit's firmware available from the Website of the drive manufacturer. If the drive was placed in a third-party enclosure, the enclosure manufacturer would have the updated firmware.
Cabling issues. USB and FireWire cable, like any other cable, can suffer internal breaks and shorts, which can show up as errors or lockups during file transfers. Make sure the cable is intact and that the connectors at both ends are not damaged.
Bus contention issues. Systems with both 32- and 64-bit PCI slots (found in many server or dual-processor motherboards) can often have bus contention issues with mass storage controllers, including USB 2.0 and Firewire controllers. It is possible to plug many 32-bit PCI controllers into 64-bit slots, so if transfers of large amounts of data to external drives freezes the system, try moving the controller to a 64-bit slot if one is present.
Known issues. Finally, and most predictably, Windows 2000 and XP have some known issues with 1394 and USB 2.0 devices and host controllers. A search of the Knowledge Base using "1394" or "USB" and "fix" should turn up the latest batch of pre- and post-Service Pack fixes for 1394 / FireWire and USB 2.0.
Serdar Yegulalp is editor of The Windows Power Users Newsletter. Check it out for the latest advice and musings on the world of Windows network administrators -- and please share your thoughts as well!