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Is parity-check/-rebuild single threaded?


hawihoney

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Posted

This is normal, I get around 160MB/s writing to my test server with 30 devices, it's much faster if I remove some devices, while keeping dual parity. 

  • 1 month later...
Posted (edited)

AMD user here. Looks like I should have searched harder before posting my thread about the same issue. I also am capped about nearly the same speed. Granted my hardware isn't as good as OP, but still I think there may be something in common here.

Difference with mine is that i don't see a specific core maxed out at 100%, but I do see unraidd0 sitting at 95% cpu according to top. Is that normal?

 

 

Edited by johnsanc
  • 3 weeks later...
Posted

I faced the same problem in my project:

 

Now I like to know:

As the performance is not good, it seems Unraid is not using the CPUs offload engine to accelerate XOR calculations. If this is the case: Why? I mean yes, HDDs were slower in the past than CPUs, but today it is easy to reach the limit with the right amount of HDDs. And what about a future proof setup for SSDs? And what about energy efficiency? An accelerated calculation is an easy task for the CPU which does not waste energy and keeps it cool.

 

More information about XOR offloading:

https://www.kernel.org/doc/Documentation/crypto/async-tx-api.txt

https://www.snia.org/sites/default/files/SDCIndia/2017/Slides/Vikas Aggarwal - Cavium - Hardware acceleration for RAID5-6 V2.pptx.pdf

 

 

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