The controllers provide independent PHYs. Each PHY supports SAS link rates of 3 Gb/s, 6 Gb/s, and 12 Gb/s, and SATA link rates of 3 Gb/s and 6 Gb/s. Each of the controller PHYs connect to one controller port.
Direct connect (port-to-port) disk drives can take advantage of the stated data transfer capability. Connecting one controller port to an expander backplane provides the maximum data transfer capability per backplane connection.
Intel® 12 Gb RAID controllers connected to a 12 Gb expander, which is then connected to 6 Gb drives, will show a 12 Gb port connection speed in the RAID configuration utilities, Intel® RAID Web Console 2, and the RAID BIOS configuration utility. This is because from the controller’s point of view, it has a 12 Gb connection to the expander. From the expander point of view, it has a 12 Gb connection to the controller but a 6 Gb connection to the drives, and the expander is consolidating the 6 Gb dataflow in and out of the drives into a 12 Gb stream in and out of the controller. So from the controller point of view, it only aware of a 12 Gb connection.
|Note||A PHY connects a link layer device to a physical medium such as a SAS or SATA cable. A PHY typically includes a PCS and a PMD layer. The PCS encodes and decodes the data that is transmitted and received. The purpose of the encoding is to make it easier for the receiver (disk drive) to recover the signal.|