User's guide for the Sonnet Fusion R400Q 4-drive Serial ATA rack mount storage system with quad interface. These directions apply to storage systems with drives.
You are using a SATA port that is not port-multiplier aware. For example, the internal SATA ports in a Mac Pro that may be brought to the PCIe rear panel via an eSATA extender cable are not port-multiplier aware. All of Sonnet's Tempo SATA cards with external ports are port-multiplier aware.
Another manufacturer's previously-installed SATA driver may be accessing a Sonnet SATA card in error causing a drive access slowdown. For example, we have seen Fusion D400QR5 performance drop from 200MB/s to under 50MB/s in such circumstances. The solution is to remove the other manufacturer's SATA driver.
