[ryao]

On my SSDs, I can go to 96% full without issue using ZoL. ZFSOnLinux is patched to disable ZFS' LBA weighting on solid state storage though. Non-solid state storage tends to reach 96% in metaslabs early due to LBA weighting, although I would be fine with filling a pool to 90% with the recent code. Going much higher than that is probably not a good idea though.

I have yet to see evidence that 60%-80% causes issues unless the system is so overloaded that having performance drop a small amount is noticeable. On spinning disks, such a thing is only natural because there is not much space left in the outer platters.

That said, older versions years ago would enter best fit behavior at 80%, which is where the 80% talk originated.