Do We Really Need To “Safely Remove” USB Devices?

Have you noticed that when you plug in a USB drive, Windows puts a little icon in the system tray informing you that you can “safely remove” the USB drive? If you click on the option to do so, Windows will then tell you that it’s safe to remove the drive. However, what does it mean to “safely remove” a USB drive? And do we need to do it with all USB devices?

What “Safely Remove” Does

safely-remove-notification

So why do we bother safely removing USB drives, and what happens if we don’t?

To understand this, we have to look at how computers use files. Let’s say you have a text document on a USB stick, and you open it up on your computer via the stick. Your computer will take the document and load it into the RAM, where you can make changes to it. If you’ve ever suffered from a power cut or computer crash, you’ll know that any changes you make to the document while it’s in the RAM is lost when the computer loses power. That’s why we use the “Save” command to save our work — it’s when the PC takes what’s on the RAM and writes it to the permanent storage of our choice. In this case, it will be the USB stick.

safely-remove-usb

The thing is, saving to a physical media isn’t an instantaneous process. The computer has to write the data from the RAM to the USB stick. What do you think would happen if midway through the writing process the USB drive was removed from the computer? Due to not completing its writing process, there’s a chance the file on the USB drive would become corrupt and suffer from data loss, if not become entirely unusable! This is what the “safely remove” feature aims to avoid, by allowing the computer to finish up its write jobs before you remove the USB drive.

In a way this is similar to if you’re hand-writing a document for someone. You begin to write the document, but mid-way through the process the person you’re writing it for says he wants the document gone and suddenly snatches it out from under your pen. Not only is the document still incomplete, but chances are it will ruin the document in the process! In a way, this is akin to what happens to documents when the USB drive is removed during a write process.

Does Every USB Device Need to Be Safely Removed?

So now we know the “safely remove” feature is designed to prevent data corruption by removing a USB drive during a write process. Therefore, this means that any device that doesn’t have data written directly onto it doesn’t need to be safely removed like USB drives do. If you want to disconnect peripherals such as mice, keyboards, game controllers, and WiFi adapters, you can simply unplug them whenever you like without fear of data loss. After all, there’s no data in question to be lost!

Playing It Safe

It can be confusing as to what “safely removing” a USB device is, but it’s actually quite simple! Now you know what it does, why it’s needed, and why it only applies to USB drives and no other USB device.

Have you ever suffered data corruption due to removing a USB drive too quickly? Let us know below.

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12 comments

  1. I can speak from personal experience that you need to safely eject the USB drive. I had a classmate in tech school who didn’t do it and just yanked the drive from the computer.

    His drive got to the point where it wouldn’t be sensed by the PC when he plugged it in. I tried to help him out and I told him to first copy the files to the PC then reformat the USB drive. After trying that multiple times and having it fail, he had to discard the drive. He paid about $50 for the drive. This was in 2007 when USB drives were more expense.

    If my drive cost 2 cents, $2 or $25 I always eject before removal because I can still see his face when I told him the drive was worthless!

  2. I’ve been pretty careful when removing USB drives, had very few corrupt files. Though you showed a “thumb drive” or “stick”, solid state thumb drives, I believe similar care should be taken with USB hard drives. Correct?

    1. I think it is best to do safe removal of memory cards too- Like SD cards etc. Might not matter if you are just downloading photos from the card and nothing was written- but I would rather be safe than sorry.

  3. Safely remove hardware is probably the biggest annoyance when using external USB storage and I blame Windows hidden file write management for it. It is basically unnecessary if you make sure to disable write caching which is a ‘performance’ enhancement that is frankly totally unnecessary when using external drives for storage.

    That being said, removing the USB stick while actually writing to it is a definite no-no and can result in the thumbdrive becoming unreadable (happened to me once, could never reuse it after that).

    It would be a BIG IMPROVEMENT of there were utilities that actually show what is accessing the drive and when, with the option to COMPLETELY PREVENT APP WRITE ACCESS at the low level when files are not being written to it BY THE USER, because as it stands now, the user has ZERO CONTROL OVER THE PROCESS. My files are MINE to manage, stop interfering!!!

    It’s high time users demanded control over their files back. I’ve been using computers since the days of the first IBM PC and deliberately crippled file management at the operating system level has got to be the biggest aggravation with modern operating systems. The most common complaint, besides forced ‘upgrades’ that mess up computers, that I hear from users, is “where did the [device’] store my files” and “why can’t I [save, copy, move] my files to’ [device]”.

  4. Have actually ‘bricked’ a USB thumb drive by pulling it out too soon.

  5. Let’s not ignore that there is VOLTAGE at the USB port.
    Safely removing RARELY works from W7 and up (it works in nearly every case for XP). There is still voltage at the port in most cases. The ‘proof’ of this is that many OLDER USB devices have a power light that indicates voltage at the port. A device should NEVER be removed if the power light is ON as not only could the device be damaged but also the USB port and circuitry on the computer.
    Many of the newer USB devices (stick drives in particular) have only an activity light that might mislead one into believing there is no power to the device.

    My best recommendation – after 41 years as a systems integrator – is to NEVER disconnect a USB stick from a computer unless the power is OFF on the computer. Other devices may vary, but I have a number of clients who have not only bricked the USB stick, but damaged the computer. Don’t be fooled by Windows.

    Tim Deaton
    BSME, MSIA DDC

    1. “NEVER disconnect a USB stick from a computer unless the power is OFF on the computer.”
      That is an asinine way of doing things!
      I am NOT criticizing what you said, Tim. I am criticizing Microsoft for designing it that way.

      In many years of using Linux I have never had a problem removing my USB stick. I click on Eject, the power light flickers for a second or two and then goes off. As far as my system is concerned, the USB is no longer there.

    2. This is inherent in the design of the connector pair. The power pins/contacts engage first and disengage last to ensure that the device is powered before the data lines on insertion of the device and powered down after the data lines have been disconnected upon removal of the device. This feature is essential in allowing the USB device to be hot swapable and achieves exactly the same result as switching power off of the computer before removing the USB device.

  6. I have had numerous issues with USB drives, especially spinning media. It is not limited to Windoz. If you pull a media library out of a smart TV other ‘smart’ device, it messes up the Master Boot Record, making the drive unreadable – either in Linux or Windows. I guess the MBR is the last thing written on the drive when data is being saved.

    Fortunately, if the file structure is NTFS (which is my default for storage media, allowing files larger than 4GB), running ‘chkdsk /f’ in windows a couple times generally corrects this and makes the drive readable again.

  7. My friend gave me a USB drive to look at, only a few weeks old and we had the conversation about safely removing the drive, he hadn’t been and the drive would not read write or format, lesson learned cos I told him that I always do without exception or carry on wasting money and possibly lose something important! regards, Ian.

  8. While pulling drives out too soon is a problem, any 3.0 or 3.1 usb drive that isn’t reading or writing does not need the safe removal. There’s nothing to corrupt because nothing is happening. And it won’t fry the drive as it used to do with usb 1.1 and 2.0.

  9. If you have a Windows USB Removable ‘Flash’ drive, it is usually safe to pull it out after the LED activity light has stopped flashing for at least 5 seconds. However some USB flash drives do not have LED activity lights.
    If you have an external USB HDD (or Fixed-disk type USB flash drive) then Windows can delay writes for 30 seconds. So if you copy a small file to the USB HDD and then remove the USB drive, you will often lose that file/data or corrupt the filesystem. If you wait 30 seconds after writing one small file, you will see the LED activity light flash (as Windows flushes the delayed cached writes to the USB drive).
    So, basically, ALWAYS use Safely Remove Hardware or Eject before removing any hot-swap device containing a writable filesystem!
    Note that Windows 10 has a nasty habit of locking a USB flash drive the first time it sees it. Safely Remove refuses to release it even if you have not written any files to it and wait one hour with all apps closed! In this case, try a 3rd party USB Eject tool – or wait 40 seconds and then pull it out and cross your fingers!

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