The Design Of High-speed SAS Storage Subsystem With Expander Technology

In recent years, the Internet services especially online video services develop rapidly. More and more Hard disks are required to storage the video resources. Obviously,8Hdds per system can't not meet the increased requirements any more. In this case, a SAS storage subsystem is designed that includes a piece of SAS RAID card, a piece of expander card and 3 pieces of SAS backplane. After the expander card is applied, the system can supports up to 24 HDDs instead of 8 HDDs.The subsystem support SAS2.0 protocol and 6Gbps transmission rate.The article describes how the subsystem is designed and debugged. This article mainly introduces the following several aspects:1) Firstly, introduce all the functions should be designed, and figure out the overall design schemes of hardware and software. In this section, introduce how to select key chipset, the solution about board interconnection and HDD status management solution.2) Secondly, introduce the Expander card how to be designed in detail including hardware and software. It releases schematics of main function modules like VR,CLK,SAS,external MEM and etc, introduce FW and mfg files how to be modified to work normally and introduce how to debug.3) Thirdly, introduce SAS backplane how to be designed and debugged. It releases schematics of key modules like SAS, summarize the key problems encountered in the procedure and the solutions.4) Lastly, the article summarizes the whole design process, figure out the creative design, analyze the root cause of failure and corresponding solution that will be done in the future design.