If it looks like the Code42 app is restarting your entire backup unexpectedly, it may actually be running a file verification scan. The scan is an important and normal part of the Code42 app's scheduled activities, but it can also be triggered by several events:
- Changing the file selection: If you update your backup file selection, either to add or remove files, the scan runs to look for new, changed, or deleted files.
- Replacing your device: After replacing a device (for example, if you recently changed devices), the scan runs to compare the files on your device to the files in your existing backup archive.
- Clearing your cache: The cache includes information about your destinations and the data on your device. When the cache is cleared, a file verification scan initiates to help rebuild this information.
- Attaching an external drive: When you attach an external drive, the scan runs to compare the files on the drive to the files in your existing backup archive.
- At device reconnection: If the device is powered off or asleep at the scheduled scan time, the scan runs 30 minutes after the device reconnects.
- Manually: The file verification scan can be triggered at any time from the Backup Set Settings Menu.
The file verification scan inspects your file selection for any new, changed, or deleted files that real-time file watching may have missed. Think of it as a second line of defense for detecting changes to your backup file selection.
After the file verification scan completes, CrashPlan may require additional file information validation tasks be performed, such as Data Deduplication.
Data Deduplication is the process of comparing local scan information with the data which is stored in the cloud backup archive, to determine whether it needs to be backed up, either fully or incrementally. If the Code42 app determines that a scanned file is present in the cloud archive, it skips to the next file entry and repeats this process until it reaches the end of the backup file manifest. Data Deduplication will take longer to complete for large and/or complex archives, though the process will be much faster than if the Code42 app were uploading all files to the cloud again.
The Code42 app will prioritize backup data which has changed or has been added to the selection recently, meaning that deduplicating may not begin until any new or modified data has been uploaded. Once this initial ‘new data’ upload is complete, deduplication will allow the remaining portion to complete quickly. This process will resemble your backup sending files to the cloud, and displays an estimated completion time which is calculated as if all files need to be uploaded.