Today's competing non-SCSI solutions lack the features and connectivity needed to provide a comprehensive I/O interface solution. SCSI is the only high-performance interface that allows devices operating at different speeds to be connected to the same bus, and the only I/O solution that offers a method for connecting both internal and external SCSI devices. UDMA/IDE only supports two drives per channel, and can only handle a small range of internal devices.

Furthermore, although UDMA/IDE has come a long way since its initial introduction, all mission-critical storage subsystems use SCSI, as the MTBF rating (Mean Time Before Failure, the average time a product of a given design can last without requiring repair or replacement) is much higher with SCSI. As a result of these factors, all high-end harddisks use the SCSI interface.

Also, a SCSI-based system imposess much less overhead on the main CPU because all data I/O and the controlling and device handling is handled primarily by the adapter, which frees the CPU to fetch data and run applications.

Overall, while lower cost makes UDMA/IDE viable for less demanding computer environments such as basic desktop PCs, it lacks the power and the broad range of connectivity features needed by workstation or server configurations.