Error Messages - Frequently Asked Questions
    
    
    Apache uses the sendfile syscall on platforms
    where it is available in order to speed sending of responses.
    Unfortunately, on some systems, Apache will detect the presence of
    sendfile at compile-time, even when it does not work
    properly.  This happens most frequently when using network or
    other non-standard file-system.
    Symptoms of this problem include the above message in the error
    log and zero-length responses to non-zero-sized files.  The
    problem generally occurs only for static files, since dynamic
    content usually does not make use of sendfile.
    To fix this problem, simply use the EnableSendfile directive to disable
    sendfile for all or part of your server.  Also see
    the EnableMMAP, which can
    help with similar problems.