SAS 4.0 (22.5Gbps) challenges for server platforms

Today's varied server applications necessitate a variety of storage requirements. The advent of SAS 4.0 technology represents an evolutionary advancement in storage IO to meet the growing demands of today's storage environments. With unprecedented performance levels and improved signaling and management for supporting larger disk attach, SAS 4.0 offers users a much more scalable and flexible direct attach storage (DAS) interface. This paper highlights the signal integrity challenges faced when designing SAS 4.0 links at 22.5Gbps. Cable skew, connectors, material loss and via stubs affect the channel to a great extent. Signal integrity analysis is performed at SAS 4.0 speed to quantify the impact of above listed parasitic effects.