I haven't written low-level code for Windows for a while, but I recall that all Windows I/O since the NT days has been asynchronous at the kernel level. An I/O

I haven't written low-level code for Windows for a while, but I recall that all Windows I/O since the NT days has been asynchronous at the kernel level. An I/O thread is purely an user-space construct. In Linux, I/O threads are real, with true asynchronous I/O only being recently introduced with io_uring.