Data Backup Digest

With Windows and other operating systems, there is an option to "eject” your USB drive on a software level before physically removing it. After doing this, Windows will tell you that it is now safe to remove your USB drive or device. But what does this do, and why is it important to do it? If you are using external USB drives, be they flash-based or hard disk drives, it’s worth understanding how to eject drives after you are done using them and why you should.

Write Caching
When data is written to a disk, be it an internal one or an external one, the operating system uses something called a “write cache.” This is a sort of buffer area on a system disk where data is temporarily saved before writing it to the target location. This is used with USB drives to account for the relatively slower USB data transfer speeds.
The danger with write caching is that if power is lost or communication with a device is lost during a data transfer, there may be unwritten data that’s still stuck in limbo in that cache. When this happens, it can cause the target disk to be corrupted.

Safely Ejecting Media
In Windows, the default setting is to mount removable drives with write caching disabled. This is to decrease the chances of corruption occurring due to an interrupted transfer with data still in the cache. However, it does not eliminate the chances. Corruption may still occur with write caching disabled. This is particularly true if a removable device is being accessed or written to when it is removed or when power is lost.
When a USB device is connected in Windows, a USB icon with a green check mark will appear in the system tray. Clicking this icon lets you choose a device to be safely removed. When you do this, the cache is flushed and Windows ensures that no write operations are currently underway. This allows you to remove the drive safely.
In Linux and Mac OS X, write caching is not disabled by default. For this reason, it’s even more important to dismount or eject your removable media before physically removing it from the machine. In OS X, you can click the eject icon next to the drive in the Finder window. In Linux, you can click eject in the graphical window environment, or you can use the umount command from the command line interface.
Other Devices
For devices other than computers, such as digital cameras, game consoles, digital picture frames and smartphones, there may not be an option for safely ejecting the media. If in doubt, it’s a good idea to power down the device completely before removing any SIM cards or detaching an external drive or USB thumbdrive. Similar to PCs and laptops, other consoles and devices that use removable media can also cause corruption if they are not safely removed.
In conclusion, it’s important to mount, unmounts and connect or disconnect your drives properly. This is especially true with the media and disk drives you’ll be using for data backup purposes. Corrupting your backup drive can be devastating, and taking an extra step of precaution is worth the reduced risk of data loss.