Steve Litt <slitt@???> wrote:

> I did a test. I created hello.txt, put "hello world" in it, saved it,
> and yanked out the thumb three seconds later. Of course the
> whole /media/sdd1 tree vanished. When I plugged in the thumb again,
> hello.txt contained exactly what I'd typed in it. Now of course, this
> is an anecdote, not a mathematical proof or a statistical study, but it
> does point to the possibility that sometimes all your stuff gets
> written to the thumb and everything's OK when you yank.

Timing is everything.
When you write data to disk, it initially goes into the write cache as a dirty page. Unless the user (or their program) explicitly syncs that out, then there it sits until ...
The cache gets written out when the background system processes clean up and write the dirty pages out to disk. How long this takes depends on tuneable kernel parameters and how busy the system is. If the system, and in particular the storage, is otherwise idle then IIRC your small file will get written almost instantly. If the system is really busy, with a large dirty cache, then it'll take a lot longer.
As another test, try running "cat /dev/zero > /media/sdxn/testfile" then save your new file and immediately pull the drive.

This page seems to be a decent writup :
http://www.westnet.com/~gsmith/content/linux-pdflush.htm


It's not something I've every fiddled with on Linux, but I do recall hearing an "interesting" tale of a SCO Openserver admin who didn't know what a process was and got rid of it. This was the cache flushing daemon - and he found out the hard way, when the system crashed, what it did ...