Run a Windows program which writes to disk and the changes won’t necessarily be saved immediately. The OS holds them in its cache for a short while, then writes them all at once in an optimized order to improve performance.

While that seems like a smart speedup move, it can also cause problems. Unplug a USB key before all the changes have been corrupted and the drive could be corrupted.

FFB is a tiny console- based tool – a 26KB download – which tells Windows to flush the write cache of one or more storage volumes immediately.

There’s no need to learn a complicated command-line syntax, because all you have to do is tell the program which drives to flush, and it doesn’t even care how they’re described. Drive letters, drives or mount points will all work properly.

Here are a few examples.

FFB C
FFB C D E
FFB C: E:
FFB D:\ E:\
FFB C:\CardReader\SD
FFB \\?\Volume{16b5dd59-158f-11e1-b349-00166f0dc865}

There are a couple of switches which dismount the drive as well, effectively turning it into an “eject” tool.

This command asks Windows to dismount a drive if it can:

FFB E: -d

And this command tells Windows to dismount a drive whether it’s being used or not.

FFB E: -f

That’s a drastic move which makes open handles invalid and could cause all kinds of problems, including crashes. But if a program is hanging on to the drive and can’t be closed, it might be worth the risk.

FFB is a geeky freeware tool for Windows 2000 and later.