Apparatus and methods for multiple unidirectional virtual connections among SAS devices

A method operable in a serial attached SCSI (SAS) domain having a SAS expander coupling a first SAS device to each of second and third SAS devices, the method comprising:

• establishing a first virtual connection between the first SAS device and the second SAS device through the SAS expander wherein the first virtual connection is established by the first SAS device and is used to transmit frames from the first SAS device to the second SAS device;
• and
• establishing a second virtual connection between the first SAS device and the third SAS device through the SAS expander wherein the second virtual connection is established by the third SAS device and is used to transmit frames from the third SAS device to the first SAS device,
• wherein the first virtual connection and the second virtual connection may overlap operation, and
• wherein the first and second virtual connections utilize the same physical link (PHY) coupling the first SAS device to the SAS expander.

A serial attached SCSI (SAS) expander adapted for coupling to first, second, and third SAS devices wherein the SAS expander further comprises:

• first virtual connection logic adapted to establish and operate a first virtual connection between the first SAS device and the second SAS device for purposes of transmitting frames from the first SAS device to the second SAS device;
• and
• second virtual connection logic adapted to establish and operate a second virtual connection between the first SAS device and the third SAS device for purposes of transmitting frames from the third SAS device to the first SAS device,
• wherein the first virtual connection logic and the second virtual connection logic are each adapted to allow the first virtual connection and the second virtual connection to overlap operation utilizing a single physical link (PHY) coupling the SAS expander with the first SAS device.

A serial attached SCSI (SAS) end device comprising:

• first virtual connection logic adapted to establish and operate a first virtual connection between the SAS end device and a first SAS device through a SAS expander for purposes of transmitting frames from the SAS end device to the first SAS device;
• and
• second virtual connection logic adapted to establish and operate a second virtual connection between the SAS end device and a second SAS device through a SAS expander for purposes of transmitting frames from the second SAS device to the SAS end device,
• wherein the first virtual connection logic and the second virtual connection logic are each adapted to allow the first virtual connection and the second virtual connection to overlap operation, and
• wherein the end device is adapted to establish the first and second virtual connections on the same physical link (PHY) coupling the SAS end device to the SAS expander.