This article answers frequently asked questions about how CloudM ensures your files are migrated without corruption including details around how we use file hashes and what they are.
1. What is file hash validation?
Think of a hash as a unique digital "fingerprint" for a file. Hash validation is the process of comparing a file's fingerprint before and after we move it. If the fingerprints match, we know the file has been transferred perfectly without any corruption.
2. How does CloudM check my files during a migration?
Our migration platform follows a strict, automated process to validate every file:
- Record Hash: During the initial scan of your source system, we record the original hash of each file.
- Download and Re-Check: When we download a file to migrate it, we immediately calculate a brand new hash from the downloaded version.
- Compare: We then compare the original hash to the new hash.
- A match confirms the file is intact, and we proceed to upload it to your destination.
- A mismatch triggers our error-handling process.
3. What happens if a file's hash doesn't match?
A hash mismatch indicates a potential problem. Our system automatically takes the following steps:
- Automatic Retry: We will try to download the file again and repeat the hash comparison. This often resolves temporary network issues or platform delays.
- Migration Failure (Safeguard): If the hashes still don’t match after our retry attempts, the migration for that specific file will fail. This is a critical safety measure to prevent a corrupted or incorrect version of a file from entering your new environment.
4. Why would a file's hash change or not match?
A mismatch is rare, but it can happen for a couple of common reasons:
- File Was Modified: The most common reason is that a user edited and saved the file on the source platform after our initial scan recorded the original hash.
- Microsoft 365 Latency: For some older files on Microsoft 365, a hash might not be immediately available from Microsoft's servers. Our retry process typically resolves this once the hash is generated.
5. How do I know if a file failed because of a hash mismatch?
If a file fails this validation check, it will be clearly marked in your migration report. You will see the specific item logged with the following error message:
Source file hash: [SOURCE_HASH] does not match downloaded file hash: [DOWNLOAD_SOURCE_HASH]
This allows you to easily identify any files that were not migrated due to this integrity check.