Lighttpd

so dont use sendfile if the underlying FS does not support it.
it is runtime configurable setting.

http://trac.lighttpd.net/trac/wiki/server.network-backendDetails

you have to use writev than.

It's the server's job to switch as necessary. It's terrible to require this to be configured manually, when there's a clear, explicit error return from the syscall that can be used to detect it.

This is a very old ticket, but is marked High Priority.

On some systems, some filesystems support sendfile() and some do not. If lighttpd is configured to use sendfile() as the backend -- which is a global setting in lighttpd and not configurable per filesystem -- it would be nice if lighttpd could fall back to write() if sendfile() failed with EOPNOTSUPP. (feature request)

Please downgrade priority and mark this ticket as Feature Request.

This ticket should not be High Priority (and a 7-year-old ticket obviously wasn't :)) since there is a simple workaround: if you need to serve some files from a filesystem that does not support sendfile(), then do not use the freedbsd sendfile network backend in lighttpd.conf.