One note about sendfile - if you are using VirtualBox and serving files out of a shared folder with nginx (or I assume Apache) you'll need to disable it or you won't see any updates you do to files once the first version is sent.
This VirtualBox bug was the reason that I started reading more about sendfile and encountered this article about nginx optimizations. The bug actually causes really weird behavior, in which extra bytes are added at the end of the file.
It doesn't really add extra bytes - it "remembers" the original size of the file. So if you update the file to be larger, you only get the first N bytes. If you update it to be smaller, you get the full file + zero bytes at the end to fill out the remainder. If you can't turn off sendfile for some reason, the workaround is to delete the file every time before saving it.
Thanks, enlightening. And is this because due to some implementation difficulties for sendfile when using shared file system between the box and the host machine?
Haha omg this issue. I came across this about a year ago, and it took forever to diagnose the problem. Who would think to look for a specific declaration in the web server config? I thought for the longest time it was a problem with my host<->guest mount. Glad to see other people suffering similarly :p
Not only that, but using an nginx container on OSX with boot2docker (VirtualBox based) was actually just causing all of the static files being served to be truncated. I spent a solid day tracking that down.
