Safely Removing USB Flash Drives

The Ohio State University at Lima
Technical Bulletin #200710160730

There is a procedure to removing USB flash drives from the computer when you are finished working. Simply unplugging the drive is not enough; if the proper procedure is not used, data loss can occur.

The operating system (Windows or Mac) often employs a technique called "delayed writing". By waiting to write data to a drive (hard drive, network drive, or USB drive) as a background activity, the system will appear to be more "responsive" to the user, and the user does not have to sit and wait for the system to write the data.

When ejecting drives, or unplugging flash drives, you must tell the system that you are about to unplug the device, and it should finalize the data it needs to write out. If the system is not informed of the coming action, it may try to write data out when the device is not present, and any data not yet written will be lost.

(Windows) In the lower right hand corner in the system tray area, there will be a small picture representing a device with a green arrow pointing down and to the left. When you are ready to unplug the device, click on that icon, and the Safely Remove Hardware wizard will appear. Select the device you wish to remove, and wait for Windows to write its data and inform you that it is safe to remove the device.

(Mac) In a finder window, select the drive, and click the eject/unmount button that appears next to it. Alternatively, you can drag the device icon from the desktop over the Recycle Bin, which will unmount the drive and make it safe to remove (just like ejecting a CD).