Most of us don’t have the patience to eject our USB flash drive or other removable media after we are done using it, we just unplug it.
It’s a good practice to eject your drive before unplugging it, the reason is because operating systems use a process called write caching. The operating system doesn’t always write a file to a drive immediately, but instead caches it and waits until it has multiple write operations to complete.
Doing these all at once improves performance, but if the cache is still full when you remove the drive, your data will become corrupted. Clicking the Eject button causes the cache to be emptied and any remaining data to be written to the drive.
That’s the reason why there’s often a delay of several seconds between ejecting the drive and being notified that it’s safe to remove it.
There are also potential issues with the abrupt removal of the power supply from a flash drive. Flash memory is susceptible to this, and it can cause parts of the drive to become corrupt. if you’re used to unplugging without ejecting your drive you will end up having this message when you connect your drive to a computer.
This means your file system has been corrupted and you can’t access your data. There are several ways of solving this problem but here is one that has once worked for me.