Ask LH: Do I Really Need To Eject USB Drives Before Removing Them?

Dear Lifehacker, Some of my computers (like my Mac) are always warning me about disconnecting flash drives without ejecting, while Windows doesn't seem to have a problem — in fact, my external USB drive doesn't even have an eject option. Does this mean it's safe? How do I know when I actually need to eject a drive?Sincerely, Concerned About Corruption

Dear Concerned,

This is one of those questions that has a short answer and a long answer. The short answer is this: you should probably always eject a drive before removing it, even if the context menu doesn't have an eject option. Mac and Linux will always provide you a way to eject a drive, but like you said, sometimes Windows doesn't have an obvious "eject" button for certain drives. On Windows, click the "Safely Remove Hardware" icon in the system tray, choose your drive from the list, and then remove it once it notifies you of its safe removal.

Now, the long answer: In Windows, you can sometimes remove a flash drive without ejecting. Here's a bit more information on how computers deal with USB drives.

Why Computers Want You To Eject Drives

Obviously, yanking out a drive while it's being written to could corrupt the data. However, even if the drive isn't actively being written to, you could still corrupt the data. By default, most operating systems use what's called write caching to get better performance out of your computer. When you write a file to another drive — like a flash drive — the OS waits to actually perform those actions until it has a number of requests to fulfil, and then it fulfils them all at once (this is more common when writing small files). When you hit that eject button, it tells your OS to flush the cache — that is, make sure all pending actions have been performed — so you can safely unplug the drive without any data corruption.

Why Windows Doesn't Bug You To Do It

Mac and Linux use write caching on pretty much every drive, and will let you eject any drive through your file manager. Windows, however, is a bit more mysterious on this front. It actually disables this write cache feature for drives it sees as "removable", because it knows people are likely to yank them out without ejecting. As such, disabling this feature on removable drives decreases the chance of data corruption. It keeps the cache enabled on non-removable drives, though — and sometimes it recognises external USB drives as not removable, which is why your USB drive doesn't have an eject button. Paradoxically, it's also why you need to eject that drive: since Windows doesn't see it as removable, it has enabled the write cache for it, increasing the chance of data corruption.

You can edit the write cache settings for any drive from the Device Manager. Just expand the Disk Drives section, right click on the drive you want to edit, and hit Properties. Go to the Policies tab, and click the "Quick Removal" radio button to disable the cache (or click "Better Performance" to enable the write cache).

Why You Should Probably Manually Eject All Your USB Drives Anyway

So, unlike OS X and Linux, Windows has a few precautions in place for preventing data loss. However, the write cache isn't the only thing that can cause data loss. Have you ever tried to eject a drive and gotten a "drive is in use" error? Sometimes there's something going on in the background you don't know about, or sometimes a program is just being silly and has still locked a file on the drive even if it isn't using it. If you were to yank it out during one of these situations, you could still cause data loss. Ejecting it will warn you of the situation, and let you close the program in question (or use something like previously mentioned Unlocker to unlock the in-use file).

In the end, there's no reason not to eject your drives, and doing so will ensure you're USB drive's data is uber-safe. Windows users may be less likely to experience issues due to the way Windows handles removable drives, but they aren't 100 per cent protected. Ejecting the drive is a great habit to get into, since without it, you wouldn't always know if it was safe to remove or not.

Cheers Lifehacker


Comments

    Keep in mind that you may corrupt the entire dive if you yank it out while the OS is making changes to the file system tables on the drive.

      ME, this happened to me on a 300GB drive...i accidentally unplugged it from the wall and it instantly died

      Need to be clear here. USB thumb drives versus external USB hard disks. As stated below, thumb drives likely no problemo but ext HDD, you're asking for trouble if you yank one of them.

    I have never once used the eject option in windows, and never had a corrupt data issue either, in about a decade.

      I've had end users give this "excuse" many times.
      One guy in particular made a very big deal about it when I pointed out that he should always eject - that very same day I ended up spending literal hours running recovery software on his un-ejected drive when he came back thinking he'd lost months worth of work.

      I used to but i stopped that a few years ago, and never had a problem.

      The other week my GF unplugged the power from a USB HDD accidently while i was copying 200GB of data over, i plugged the power back in, it didnt appear in explorer, un/replugged the USB and it was fine, continued where it left off.

      Score 1 for windows's implementation (never had a USB drive show up as non-removable, must be a dodgy USB brand if i got one that did that id take it back).

      It only takes 1 huge corrupted drive full of work to make you regret it. Obviously everyone who started ejecting their drives because of data corruption used to think just like you.

    Windows 7 Cares if you pull a drive out.
    That's why the next time it's plugged in a Windows 7 computer it prompts to do a scan disk.

    The other day I yanked my time machine USB drive without thinking. When I reconnected OSX ran file system checks on it for a few hours before I could use it again.

      Great Scott, a time machine. You may want to check that it didn't damage the flux capacitor

    More annoying is the seemingly arbitrary visibility of the "Eject" option when you right-click a disk in Explorer. Some disks have it, some don't, and I don't understand why this is.

    If anyone knows how to force the Eject option to always show up I'd be eternally grateful! Author?

      When you plug any usb drive into a Windows machine you'll get an icon in your system tray (bottom right of your screen).

      Click this icon and you'll have a list of usb connected storage devices.

      Click your drive and you'll get a pop-up tellin you it's safe to remove.

        Yes, that's what I currently do, but it's more annoying.

        It would be much more convenient if the right-click "Eject" choice was available on all removable disks from within Explorer. Why it is available for some removable drives and not others is unclear to me.

    Sometimes on OS X, you might eject the drive, but not know if it's actually been completely safely unmounted. But if you use Hardware Growler, it will tell when it's safe to remove it.

    Lifes too short to safely remove USB drives.

    i mostly yank my drives without ejecting but have had one or two times that they have corrupted data in the process. so now i always try to remember to eject & do so if i know there is something on the drive that i really need.

    Never ejected a drive and never had a problem.

    Then I bought a Mac, and all it does is winge that you did not eject the drive, for that and a few other reasons, my Mac now runs Windows as it main operating system.

    my general rule of thumb is that if the drive's light is flashing dont touch, when its not, do as you wish

    +never had a problem with damaged drives

    Pro tip. If you've corrupted a USB flash drive so it can't be accessed on Windows - either can't be accessed or doesn't appear in the list of drives, it may not be necessary to throw it away.

    http://www.pcworld.com/downloads/file/fid,64963-order,4/description.html

    This is a utility that recognises corrupt flash sticks and allows you to format them so they can be used again.

    You WILL lose all your data this way, but you won't need to buy a new drive.

    I believe this also works for any other type of flash stick like SD, CF etc, but I havn't tried it.

    i have had USB drives that were yanked out improperly that were then unreadable the next time plugged in (to different PC). Thought they were $(@&$'d until tried yet another PC that said the index was corrupted (or something similar to that) and did I want to fix it, so I did, it did, and no more problems on the orig PC that rejected it as unreadable first. Given I had reformatted a number of what I thought were faulty USB drives prior to this, I now ALWAYS use the eject drive process for both HDD and flash drives.

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