It depends on the OS, some OS have some way to do IO that gets around that. iouring or things like that. I don't know how Hurd does IO. Most microkernals have

It depends on the OS, some OS have some way to do IO that gets around that. iouring or things like that. I don't know how Hurd does IO. Most microkernals have methods to do IO in a different way. If they don't then likely they would pretty slow when doing I/O heavy operations.