I was hoping to share my findings and see if there might be a better approach in preventing OSX from throttling ZFS IO. My small external array has worked great for some time (>200MB/s), however it recently started to severely underperform (<10MB/s !). In trying to understand what was happening, I came to realise that OSX was throttling IO, as shown by
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fs_usage
Disabling throttling by setting:
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sysctl -w debug.lowpri_throttle_enabled=0
Although this seems to work, it is perhaps not the best solution in my view and I was wondering if you might have a better approach. Can Process/Thread IO priorities by altered via configuration in OpenZFS instead?
Thank you!