Trick is that nginx uses thread pools for non-blocking reading on the "fast" devices - you can't use coroutines/fibers, because on Linux is not reliably possible to read the regular file in a non-blocking way, as far as I'm aware, so that means that `read` in a single fiber would block entire thread until the data is fetched from the disk.

In the storage engine I'm developing/maintaining, I've been using fibers, for both network and disk IO, until people started noticing that, if number of the client grows, and if they ask a lot of data (generating a lot of disk traffic), the performance drops severely. I've moved to the thread pools, dispatching my disk IO operations there (although it's much problematic for the reads, as writes would be performed by kernel anyway, `fsync` and `close` would be operations that you still want to do in the separate thread): https://github.com/sociomantic-tsunami/dlsnode/blob/master/s...

edit: used right link for the freshly opensourced repo.