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CPU maxing out when copying to array (cache)

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My Ryzen 3600 CPU is completely maxing out when copying large files onto my array (well to the cache drive...). This was a single 40GB mkv file.

Any ideas why this is happening?  I can see iowait is super high, not sure what it means?


SSD is a Samsung 850 Pro 2TB, which although not nVME, is pretty quick still.  


System specs below


Asrock X570 Pro4


Ryzen 3600

2TB Samsung 850 Pro (cache)

14 x 14TB WD Reds (dual parity)

2 x LSI 9211-8i SAS controllers


System was just at the end of a parity sync, not sure if that's part of the issue


Ignore the resilio sync errors, i'm trying to find a way around having to share the entire root of my server to the /sync folder.  Infuriating...





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I logged the exact same issue. Copying to a non-cache enabled shared doesn't have the same issue. No-one seemed to have an answer as to why.

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I have observed similar behavior across several servers for a long time now and figured it was just a characteristic of the OS. It does this for me even as low as 35MB/s, but at the same time, I can also transfer 400MB/s, so it doesn't seem to be a bottleneck (even though I also see io wait)



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Can't confirm this... when i copy ~41GB over the 10GBit-LAN to my cache-SSD, the CPU has a load of ~18-26%

It might be hardware-related...

Edited by Zonediver

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Are you using the Dynamix TRIM plugin? Without this plugin, your SSD won’t get trimmed, which will cause high IO wait (shown as 100% cpu usage, because this is blocking the cpu). This results in speeds in the neighborhood of 35MB/s or even lower (depending on your ssd’s controller).


TRIM is a feature to erase ‘empty’ memory blocks on your SSD. This is only needed for SSDs not for HDDs, which is why this behavior is limited to writing to your cache drive ;)


You can learn more about the TRIM feature here: https://searchstorage.techtarget.com/definition/TRIM?amp=1

Edited by ssh

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