US 7,689,744 B1Granted

Methods and structure for a SAS/SATA converter

AssigneeLSI Corporation

InventorsChristopher J. McCarty, Margit C. Evensta, Timothy E. Hoglund

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Abstract

Methods and structure for enabling transparent coordination between multiple host systems sharing access to a common SATA storage device to improve bandwidth utilization therebetween in a manner transparent to each of the multiple host systems. The SAS protocol may be utilized by each of the host systems coupled to an SAS/SATA Converter. The storage device coupled to an output path of the SAS/SATA Converter is selectively coupled to one of the multiple host systems each coupled to an input signal path of the SAS/SATA Converter to the shared SATA storage device. Protocol conversion within the SAS/SATA Converter may convert between host SAS protocol exchanges and SATA protocol exchanges of the storage device. Other features within the SAS/SATA Converter may provide queuing or buffering of SAS protocol exchanges from a host system presently non-selected for coupling to the shared SATA storage device.

A circuit for coupling to a SATA storage device, the circuit comprising:

a first signal path adapted for coupling to a first host system for SAS protocol exchanges;
a second signal path adapted for coupling to a second host system for SAS protocol exchanges;
a third signal path adapted for coupling to a storage device for SATA protocol exchanges;
and
a controller coupled to the first signal path and coupled to the second signal path and coupled to the third signal path, said controller comprising:
a multiplexer for selectively establishing a communication between the third signal path and a selected path of either the first signal path or the second signal path;
a protocol converter for converting between the SAS protocol exchanges and corresponding SATA protocol exchanges;
and
a queue for queuing SAS protocol exchanges from and SATA protocol exchanges to the non-selected host system of the first host system and the second host system where the non-selected host system is not coupled to the present selected path, wherein the queue comprises a command queue for queuing SAS protocol commands received from the non-selected host system and a status queue for queuing SATA protocol information received from the SATA storage device for return to the non-selected host system, wherein:
the controller is adapted to enable the first host system and the second host system to interact with the SATA storage transparently with respect to one another, the controller further comprising:
a first state memory associated with the first signal path for storing state information based on exchanges between the first host system and the storage device during operation;
and
a second state memory associated with the second signal path for storing state information based on exchanges between the second host system and the storage device during operation,
wherein the controller is adapted to utilize the first state memory and the second state memory for the transparent interaction between the storage device and either of the first host system and the second host system.

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Abstract

Claims12