Incorrect I/O throttling when using block device files — Matt Jacobson

Matt Jacobson February 2022 Summary: Apple has a bug in its disk I/O throttling code that affects raw disk copies. I walk through my diagnosis. This week, I was restoring a slow-as-molasses 2.5-inch HDD to an SSD, as part of an upgrade for my mom's work machine. For whatever reason, the USB SATA controller I was using seems to limit me to 15 MB/s and 4 kB transfers. Not ideal when I'm transferring

[kazuhooku]

面白かった。macOSのI/Oスロットリングは64個のドメインに対して動作するけど、/dev/diskxは/devと同じドメインになり、devfsのドメインが誤って0になってる結果、デフォルトのSSDと同じドメインになる、と。でddで固まる