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CrashPlan Support

Backing Up External Hard Drives

Applies to:
  • CrashPlan for Home
Need enterprise or small business documentation?
This article is intended for CrashPlan for Home users. For Code42 CrashPlan and CrashPlan for Small Business documentation, read this page on our enterprise support site.


You can use the CrashPlan app to back up storage connected to your computer, such as an external hard drive directly attached via USB, Thunderbolt, or Firewire. By adding the contents of an external drive to your backup file selection, the CrashPlan app backs it up just like other files on your computer.


Follow these instructions to back up files stored on an external drive to another destination, such as CrashPlan Central or another computer.

  1. Open the CrashPlan app.
  2. Select Backup > Change.
  3. To back up the entire drive, check the box to the left of your external hard drive. To select only specific files or folders for backup, click the triangle next to the drive to expand its contents, then browse the contents and select the items you want to back up.
  4. Click Save.
    The CrashPlan app begins backing up the files on your external drive.

External Drive Selected

What happens if I disconnect my drive?

Your backed up files are safe when the drive is disconnected as long as your version setting for deleted files is set to Never (the default setting). When you reconnect the drive, the CrashPlan app resumes backup from where it left off. If you reconnect the drive and the CrashPlan app doesn't recognize it immediately, it is likely because the drive letter or name changed. See the troubleshooting tips below to correct the issue.

Disconnecting Drives
The CrashPlan app doesn’t distinguish between files that have been deleted from your computer and those that are temporarily unavailable because a drive is disconnected. If you disconnect your external drive, we recommend configuring the CrashPlan app to never remove deleted files from your backup archive.

Note: If your external drive isn't connected to your computer when the CrashPlan app runs the file verification scan, it's possible that your backup status will report 100%, even if there are additional files on the drive that need to be backed up. The CrashPlan app will detect the changes and adjust your backup status the next time the drive is connected.

Replace a drive

To add a new drive to replace a drive that you no longer use, add the new drive to the file selection.

Once the new drive is selected, the data on the new drive is de-duplicated against what is stored in the archive. This process is entirely automatic and no action is required on your part. The old path may display as "Missing" while the CrashPlan app performs a synchronization (file verification scan). Once the CrashPlan app displays that synchronization is complete in the progress bar, you can deselect the old drive's file path.

Best practices (Windows)

When you connect an external drive to a Windows computer, the operating system automatically assigns the next available letter in the alphabet. If the letter changes when you reconnect a drive you've been using for backup, CrashPlan won't recognize the drive. Consequently, we recommend assigning a static drive letter to your external drive.

Troubleshooting tips

CrashPlan app reports drive as "missing"

This issue occurs when the external drive is disconnected from the computer or the letter or name assigned to the drive by your operating system changes. The CrashPlan app uses absolute paths when backing up. If the CrashPlan app cannot detect a drive at the specified location, such as when it is disconnected or when the name of a drive changes, it lists the drive as "Missing". You can correct the issue by reconnecting the drive or renaming the drive to match the original drive letter or name.

External drive stops backing up (OS X)

If an external drive stops backing up on OS X, it is likely because the drive didn't cleanly unmount (for example, after a power outage, or disconnection without ejection, etc.). When this happens, the drive can leave behind a "ghost" folder in /Volumes, even though the drive is no longer mounted. When the drive re-mounts, your computer detects that the folder name for the drive is taken, and consequently appends a “1” to the drive name. However, the CrashPlan app looks for the folder with the original name, which is no longer connected. Use our troubleshooting guide to diagnose and correct the issue.