What is a Delta Migration?
A delta migration is any subsequent migration performed after a bulk migration has already been completed. Delta migrations detect new files that were not found in previous migration(s) and identify if migrated files have been modified or updated since the last migration.
CloudM Migrate can perform delta migrations for all source and destination platforms. However, there are important differences and considerations when migrating files to different destination platforms.
Important Settings:
- Overwrite updated documents: The setting Configuration > Advanced settings > Document > Overwrite updated documents is enabled by default. This controls whether updated files are re-migrated during delta migrations. Note: Permissions are always remapped in user file migrations regardless of source/destination combination, and permission changes are NOT considered "file modifications" controlled by this setting.
- Repatch existing permissions (Shared Drives): The setting Configuration > Destination > Shared drive > Repatch existing permissions controls whether existing shared drive file or folder permissions are re-patched at the destination during delta migration.
- Record document mapping: The setting Configuration > Advanced settings > Reporting > Record document mapping is enabled by default and creates mappings for re-migrated files.
What Constitutes a File Modification?
Understanding what is considered a modification is critical for delta migration behavior. The following apply across all platforms:
- Permissions are NOT a Modification: Permission changes are not considered file modifications and are handled separately from the delta migration process. Permissions are always remapped in user file migrations regardless of source/destination combination.
- Deletion is NOT a Modification: File deletion—whether at source or destination—is not considered a file modification and does not trigger re-migration behavior.
- File Deletion in Source: If a file is migrated to the destination and then deleted in the source, a delta migration will NOT delete the file from the destination.
- File Deletion at Destination: If a file is migrated to the destination and then deleted manually at the destination before a delta migration is performed, that file will not be re-migrated. It will instead be skipped as "already migrated" unless the file was modified at the source between migration runs.
Delta Migrations to Google Drive
Delta migrations of files to Google Drive will migrate any new files that were not found as part of the previous migration(s), but will also detect if migrated files have been modified or updated since the last migration.
User My Drives
Delta migrations for user My Drives detect file modifications and new files since the last migration.
File and Folder Behavior
- Modified Files: Files or folders that have been edited or have been renamed will be re-migrated and the file or folder in the destination deleted and re-migrated. This results in a new destination document or folder ID and a new Document Mapping (recorded via Configuration > Advanced settings > Reporting > Record document mapping, which is enabled by default).
- Drive Shortcuts: When migrating Drive Shortcuts, when you change the owner of the target file with the shortcut before delta migration, only the owner of the target file should be changed on destination. The shortcut file's owner won't change.
Shared Drives
Delta migrations for Shared Drives detect file modifications and new files since the last migration. Permissions are controlled by the Repatch existing permissions setting.
File and Folder Behavior
- Modified Files: Files or folders that have been edited or have been renamed will be re-migrated and the file or folder in the destination deleted and re-migrated. This results in a new destination document or folder ID and a new Document Mapping (recorded via Configuration > Advanced settings > Reporting > Record document mapping, which is enabled by default).
- Permission Re-patching: The setting Configuration > Destination > Shared drive > Repatch existing permissions controls whether existing shared drive file or folder permissions are re-patched at the destination during delta migration.
Delta Migrations to OneDrive
Delta migrations of files to OneDrive will migrate any new files that were not found as part of the previous migration(s), but will also detect if files have been modified or updated since the last migration.
Folder Rename and Move Considerations
Due to limitations of the API and platform, there are a couple of considerations when performing delta migrations of renamed and moved folders to OneDrive.
- From Google Drive, OneDrive and Box: Folder renames or moves are ignored on delta migrations.
- From File System: Renamed or moved folders are treated as new folders and migrated, along with their contents to the destination.
Delta Migrations to Dropbox
Delta migrations of files to Dropbox will migrate any new files that were not found as part of the previous migration(s), but will also detect if files have been modified or updated since the last migration.
Folder Rename and Move Considerations
Due to limitations of the API and platform, there are a couple of considerations when performing delta migrations of renamed and moved folders to Dropbox.
- From Google Drive, OneDrive and Box: Folder renames or moves are ignored on delta migrations.
- From File System: Renamed or moved folders are treated as new folders and migrated, along with their contents to the destination.