Quick answer
Not properly ejecting removable disks such as USB drives, external hard drives, SD cards, etc. before disconnecting them from your computer can lead to data loss or corruption. This is because when you eject the disk properly, it gives the operating system time to finish writing any pending data to the disk before it is removed. Improperly ejecting means this data can be lost or corrupted.
What does “eject” mean for removable disks?
On most modern operating systems like Windows, macOS and Linux, you are prompted to “eject” USB drives, SD cards, and other removable disks before disconnecting them from your computer.
Ejecting a disk initiates a process where the operating system:
- Flushes any cached writes – writes data from memory to the drive.
- Tells applications to close any open files.
- Unmounts the disk so it is no longer accessible to the OS.
- Releases the hardware so it is safe to remove.
This helps ensure no pending writes are lost and the disk can be safely removed without errors or data loss.
What happens if you just unplug the disk?
If you just directly unplug or disconnect a USB, SD card or other removable disk without properly ejecting it first, a few things could happen:
- Data loss – Any files/data that was still being written to the disk could be lost or corrupted.
- Disk corruption – If system areas of the disk were being updated, this could lead to filesystem corruption.
- Physical damage – Forcing removal while hardware is still active risks physical damage to connectors/drives. Although unlikely for USB drives.
- Application errors – Apps with open files on the drive could crash or report errors.
The main risk is data loss or corruption if pending writes are interrupted by removing the disk. Most modern operating systems use caching and buffering techniques to optimize write performance. This means even after you save a file, the data may not be written to the drive right away. The OS keeps it in memory and writes it shortly after. Ejecting ensures all cached data is flushed first.
If you don’t eject, this cached data can be lost when the disk is disconnected. This typically results in file and filesystem corruption.
Real-world examples of corruption from improper ejection
Here are some real-world examples of what can happen if you fail to properly eject removable disks:
USB flash drive corruption
If you pull out a USB flash drive while writing files, often those file transfers will fail or result in corrupted zero byte files. The filesystem on the drive itself can also become corrupt and need repairing. At minimum corrupted files, at worst the entire USB drive may need to be reformatted.
SD card corruption
Similarly, forcibly removing an SD card from a camera or other device while the card is being written to can corrupt files or make the filesystem unreadable by the device. Photos and video files may be truncated or damaged. The filesystem may need to be recreated using the standard FAT32 or exFAT formats before reuse.
External hard disk drive failure
External HDDs are also prone to corruption if not ejected properly. If system areas are being updated while the drive is disconnected, this can prevent the drive from mounting properly later. It can even lead to catastrophic filesystem damage where disk repair tools like Chkdsk or Disk Utility need to be used to fix the HDD.
Removable disk performance degradation
Forcing removal while writes are occurring causes excessive wear on removable disks. Over time, this reduces the usable lifetime of devices like flash drives and SD cards as storage cells wear out from the interrupted writes. Degraded performance, capacity loss and device failures occur over time.
When should you safely eject removable disks?
You should always eject your removable disks before disconnecting or removing them from your computer. Here are some examples:
- USB flash drive – Eject before removing from USB port
- External hard drive – Eject before unplugging USB/eSATA/Thunderbolt cable
- SD card – Eject before removing from card reader or camera
- Optical disc – Eject CD/DVD before pulling out of drive tray
The only exception is USB flash drives or HDDs that are externally powered – they can be unplugged without eject as long as the power cable is connected.
You should also eject disks before:
- Switching off computer
- Restarting computer
- Putting computer to sleep
This ensures all cached data is safely written before disk power is lost.
How to properly eject on Windows
On Windows, right-click on the removable drive icon and select “Eject”. Alternatively use the Safely Remove Hardware icon in the system tray. This will ensure data is flushed before initiating a safe removal.
You can also eject from File Explorer:
- Open File Explorer
- Right click on removable disk
- Click on “Eject”
If you get a warning that the disk is in use and can’t be ejected, close any apps with open files on the disk first before retrying the eject.
How to properly eject on Mac
On macOS, right-click on the disk icon on desktop or in Finder and select “Eject”. You can also click the Eject button next to the disk in the Finder Sidebar.
As a shortcut, you can also eject disks via:
- Dragging the icon from Desktop/Finder to Trash which will eject
- Using Command-E keyboard shortcut to eject
If you get a warning the disk can’t be ejected, quit any apps using the disk first then retry.
How to properly eject on Linux
On Linux desktops, right-click on the disk icon and select “Safely Remove Drive”. This will sync data and safely eject.
Alternatively, in the terminal you can use:
- umount /path/to/drive – Unmounts disk from filesystem
- eject /dev/drivename – Electronically ejects disk
Make sure to replace /path/to/drive and /dev/drivename with the correct path and drive name.
What happens behind the scenes when ejecting?
When you click the eject button or select eject on a disk, several steps happen in the operating system:
- Sync Disk Cache – Any data waiting in the memory cache is flushed to the drive
- Close Open Files – Any running programs with open files are told to close them
- Unmount Disk – The OS unmounts the disk from the filesystem, making it inaccessible
- Release Hardware Access – The SATA/USB/other hardware protocol is shut down
- Notify User Safe to Remove – Visual/audio cues that the hardware can now be removed
This graceful ejection process prevents data loss and allows safe removal.
What happens if you keep removing disks improperly?
If you keep removing disks without ejecting, a few issues can occur:
- More frequent data loss and corruption
- Degraded disk performance over time
- Eventual disk failure or permanent errors
- Failed mounts or inability to access disk contents
External hard disks are very prone to filesystem corruption if not ejected properly before disconnecting.
Frequent removable also reduces the usable lifespan of Flash drives and SSDs in particular, due to excess writes causing premature wear.
How to recover data after improper removal
If you removed a disk without ejecting and now cannot access the files, try these steps to recover the data:
- Reinsert Disk – Reconnect the USB drive or SD card to computer
- Try Mounting – See if disk mounts properly and files can be accessed
- Check Errors – Check dmesg/logs for disk errors indicating corruption
- Repair Filesystem – Run fsck in Linux/Unix or Chkdsk in Windows to check/repair filesystem
- Disable Auto-Mount – Try mounting disk manually without auto-mount
- Format Disk – If disk is corrupt, reformat (will erase data)
- Data Recovery – Use data recovery software to rescue files from corrupt disk
If the filesystem is corrupted, data recovery software offers the best chance to rescue your files from the drive and copy them to a new properly working disk.
How to avoid corruption by always ejecting
Get in the habit of always properly ejecting your removable disks before disconnecting them to avoid data loss.
- Make it part of your routine to always eject first
- Set reminders if you have a habit of forgetting
- Display a visible warning sign as a reminder to eject
- Use automated sync tools that always eject after sync
Developing the habit of ejecting disks first before removing them can save you from lots of potential data loss headaches in the future.
Conclusion
Forgetting to eject removable disks before disconnecting them can corrupt your data due to interrupted writes. Always eject USB drives, SD cards, external hard disks, etc properly after use to ensure all cached data is written. This prevents file and disk corruption issues by allowing the operating system to fully flush and prepare the disk for removal. Get in the habit of always ejecting and waiting for the safe removal notification to avoid costly data recovery scenarios. Following proper eject procedures each time protects your valuable photos, documents, and other data.
