The only time it is unsafe to remove a USB drive is if there is unwritten data still being cached (write-caching) or if it is in the process of being written too.
Problem is, that's more theoretical then in practice. USB is supposed to be a hot-pluggable protocol- the drives should be able to be added and removed as easily and safely as floppy disks (you don't have to "safely remove" a floppy disk).
The way most modern OS's handle USB mass storage is terrible, IMO; Most of them call them "removable drives" and yet institute write-caching of those drives as if they were fixed disks that couldn't be removed, not disks that could be removed at a moments notice. The idea is to "increase performance" of those drives, but it's pointless to write data faster if that data isn't safe. What makes it worse is that the cache policy is terrible as well, in that no matter how long you wait idle, the cache is never emptied- this can be tested since you can write files to a removable drive (with write-caching enabled) and wait several hours before removing it, and the data will still be corrupted. (of course thankfully write-caching is no longer a default) Thing is, that's not a cache- it's a useless buffer. A cache with a bad policy is just another name for a memory leak. Evewn the DOS smartdrv understood this, and even with all write caching options enabled the data was written within a few seconds; and if you wanted to be really sure you could simply run smartdrv /c to clear the cache manually before powering down.\\I think the entire problem with mass storage USB devices is that there is a tendency to "over-optimize", in complete objection to the very concept of a "hot-swappable" drive.
This "over-optimization" is clear, since there are now at least two options you can set for removable flash drives; disabling write-caching, and "optimize for quick removal" thing is, what is the difference? the only one that should cause problems for removal is write caching so is "optimize for quick removal" simply disabling write caching for that drive? And if so, why did they not label it "disable write caching(Optimize for quick removal)" or something similar?
The program in question seems, odd. The windows "safely remove" applet checks if there are open handles, and if so, simply says the drive is in use. otherwise, it dismounts it. if the "USB Safely remove" program allows you to "safely remove" the device while there are still open handles, then it is only fighting half the battle; the only certain thing is that most of the data that was written is still on the drive, and that the filesystem is not corrupted; file data may be lost since it probably forces handles closed that applications are using, which could in and of itself cause other applications to crash. This doesn't even begin to touch on the fact that it doesn't make simply removing the drive without "warning" any safer, since the applet can't possibly know you will remove the drive. The best it can do is disable write caching, which you can do in windows anyway.
Whenever I remove a drive and the safely remove applet refuses to allow it to be removed, I run handle with the drive root path as an argument in cmd- such as "handle L:\" which will tell me which programs have files open, and I can close the files in those applications with ease. I'm sure there are GUI tools that could be used as well (Process Explorer could be used here as well). Of course that doesn't address what I feel is the worst problem- and this is hardly specific to windows, - The fact that you even need a "safely remove" option; aside from maybe determining wether the device is safe to remove, there is no purpose for it to exist. How is a flash drive really any different from a Floppy disk? You don't have to "safely remove" floppies, the very idea of doing so is absurd, and yet we accept it with Flash drives, which are, by definition, supposed to be "hot-pluggable".
