Skip to main content

This article applies to Code42 for Enterprise version 4.

Other available versions:

Version 6 | Version 5icon.qnmark.png

Code42 Support

Back up to an external drive

This article applies to Code42 for Enterprise version 4.

Other available versions:

Version 6 | Version 5icon.qnmark.png


Backing up to a drive connected to your computer is a great addition to any backup plan. Because the drive is directly connected to your computer, backing up and restoring from the drive is always faster than using online destinations. This tutorial provides step-by-step instructions for backing up files to an external drive.


  • Speed: While backing up and restoring over the Internet can take some time, backing up to an external drive is much faster. This means that if your computer fails, you can restore the important files that you need in a fraction of the time.
  • Accessibility: Since you are backing up to a drive that you own, the option to restore your files is always within reach.

Folder destinations
You cannot set a backup archive size limit for folder destinations with the CrashPlan app. Make sure your destination folder or drive has enough space for your backup. If you run out of space at the destination, you can move the archive to a new location.


Follow these instructions if you would like to back up the files on your computer to a folder on your computer or external drive.

  1. Open the CrashPlan app and go to Destinations > Folders
  2. Choose Select

Destinations > Folders

  1. Select the device or folder to which you want to back up and click Ok
    The new destination appears in the list of available folders

Select Directory

  1. Select the destination folder to which you want to back up
  2. Click Start Backup
    CrashPlan begins backing up your file selection to the external drive.

Start backup


What happens if I disconnect my drive?

You can disconnect external drives at any time, and for any length of time—CrashPlan won't delete the files. When you reconnect the drive, CrashPlan resumes backup from where it left off. If you reconnect the drive and CrashPlan doesn't recognize it immediately, it is likely because the drive letter or name changed. See the troubleshooting tips below to correct the issue.

How is my backup archive stored?

Your backup is stored in a folder labeled with the 18-digit computer ID that corresponds to the computer being backed up. The folder contains all of the elements of your backup in an encrypted archive format.

What happens if my drive becomes full?

If a drive becomes too full for CrashPlan to continue backing up to it, the CrashPlan app reports Out of space at destination. To continue backing up, you can either move the backup archive to a larger drive, or reduce the size of the archive. Review our troubleshooting article for full details.

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 "destination unavailable" for external drive

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. CrashPlan uses absolute paths when backing up. If the CrashPlan app cannot detect a drive at the specified destination, such as when the drive is disconnected or when the name of the drive changes, it reports "Destination unavailable". You can correct the issue by renaming the drive to match the original drive letter or name.

Backup to external drive stops (OS X)

If backup to an external drive stops working on a OS X, it is likely because the drive didn't cleanly unmount (for example, after a power outage, or disconnection without ejection). 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, CrashPlan looks for the folder with the original name, which is no longer connected. Use our troubleshooting guide to diagnose and correct the issue.