If you install nginx compiled with aio support on non-aio enabled kernel, it doesn't work:

2011/04/15 11:46:25 [emerg] 18942#0: io_setup() failed (1: Operation not permitted)
2011/04/15 11:46:25 [alert] 18938#0: worker process 18942 exited with fatal code 2 and can not be respawn

All workers die, only master process remains, requests aren't served