Here are known issues when migrating content into OneDrive and SharePoint. Folders or files affected by either of these known issue may be NOT be migrated. Content sources that exceed the below limitations will have to be modified prior to the content being migrated into OneDrive and or SharePoint.
Folders containing 10,000 or more items.
LIMITATION: No single folder can contain more than 10,000 files or folders.
PREVENTION: Before migrating content from file system, rearrange your files so a single folder contains less than 10,000 items (files or other folders).
REMEDIATION: If a migration fails to complete due to too many files in one folder users will need to remediate the source content by moving items into sub-folders until each directory contains less than 10,000 items.
Recommendations: Account owners should walk through the sub-folders to locate any folder which contain > 10,000 documents/subfolders and rearrange them into other folders. There can be more than 10,000 files under a parent folder but no single folder can contain more than 10,000 files/folders.
File paths with more than 400 characters
LIMITATION: A file systems being migrated into OneDrive/SharePoint cannot contain more than 400 characters in the folder path (after the folder path is decoded into a URL).
PREVENTION: Before migrating content from a file system, shorten the names of files and folders and avoid using spaces or special characters which are decoded into addition characters that count against the 400-character limit.
For example, if the file URL in SharePoint is:
https://nuwildcat.sharepoint.com/sites/test/Shared Documents/Promotion Materials/Book&and$and@and.xlsx
The URL is decoded into this: https://nuwildcat.sharepoint.com/sites/test/Shared%20Documents/Promotion%20Materials/Book%26and%24and%40and.xlsx
REMEDIATION: Rename files and folders using shorter names avoiding spaces or special characters.