Hello all. First of all thanks to an older patch from Kumar Sundararajan and Dan Williams that helped me to understand RAID6 logic inside md better. Everything is based on ideas & discussions that started with http://marc.info/?l=linux-raid&m=136624783417452&w=1 So once again. Implement RMW support for RAID6. This time improve syndrome calculation too. The logic was split into very small parts. Each having a detailed explanation about what is going on. A few things to note: 1) Patches are based on official 3.16 kernel git. 2) The required optimized syndrome functions were implemented if possible. Generic & SSE2 are the ones that I could write & test on my machine. If you want to test/benchmark this patch ensure that you force select one of the two. Programmers with appropriate hardware in their hands are encouraged to send the missing algorithms. 3) raid6 test program was enhanced to verify algorithm correctness. This first release is based on single threaded tests writing blocks with random data and size directly onto the /dev/mdX device using dd. Afterwards a md check run verified consistency of the array. So we are in need for experienced stress testers. 4) With only a VM on my laptop available I have no real benchmark numbers. They should be on par and sometimes even higher (or less CPU consuming) than the old patch because of the syndrome redesign. Maybe testers can contribute some numbers. Any kind of feedback appreciated. Markus
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