Fix Cloud Backup Verification Failures — Ensure Data Integrity with RcloneView

April 13, 2026 · 4 min read

Senior Engineer

Checksum mismatches after a cloud transfer can indicate provider differences or real corruption — understanding which scenario you're dealing with determines the right fix.

After a large backup completes, you may encounter verification failures: checksum mismatches, files marked as different when they should be identical, or errors in RcloneView's comparison tools. These failures can have several causes, from benign provider metadata differences to genuine data corruption. This guide walks through diagnosing each scenario and applying the correct fix.

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Understanding Checksum Types

Different cloud providers support different checksum algorithms. AWS S3 uses MD5 (for standard uploads) and SHA-256 (for checksums). Google Drive uses MD5. Backblaze B2 uses SHA1. Dropbox uses a custom block hash. When rclone compares files between two providers using different hash algorithms, it falls back to size comparison and modification time instead of a hash comparison.

This means a "mismatch" in RcloneView's Folder Compare view may not indicate corruption — it may indicate that the providers use incompatible hash types and rclone is comparing by size only. Genuine corruption shows up as matching sizes but different hash values on the same algorithm.

Using Folder Compare to identify backup verification failures

Enable Checksum Verification in Sync Jobs

To catch real corruption at transfer time, enable checksum verification in your sync job settings. In RcloneView, open the job and go to step 2. Enable the checksum option. With this enabled, rclone computes and compares hashes during transfer. If a file's hash doesn't match after upload, rclone retries the transfer.

Note: enabling checksum verification increases CPU usage and transfer time slightly, but it catches data corruption that would otherwise go undetected.

Enabling checksum verification in RcloneView sync job settings

Using Folder Compare to Detect Mismatches

After a backup completes, open Folder Compare in RcloneView. Point one side at your source and the other at the backup destination. RcloneView shows files in three categories:

Match: same on both sides
Source only: exists at source but missing at destination
Destination only: exists at destination but not source
Different: same name but different attributes (size, hash, or modification time)

Files in the "Different" category warrant closer inspection. Download and compare a sample to determine if the content is actually different or if it's a metadata artifact from the provider.

Running a Check via Terminal

For a deep integrity check, RcloneView's Terminal tab lets you run rclone commands directly. Use rclone check to compare source and destination thoroughly:

rclone check source:path destination:path --one-way

This command lists every file that differs between the two sides, using the best available hash for each provider. The output shows exactly which files have mismatches, making it easier to identify whether the issue is systematic or isolated.

Running rclone check command in RcloneView Terminal

Re-Running with Different Settings

If verification failures persist and the files genuinely differ, re-run the backup job with:

Checksum verification enabled: ensures rclone re-transfers and validates
Ignore existing: force re-transfer even for files that appear present
Low level retries increased: gives more chances for successful transfers

For cross-provider backups where hash algorithms differ, switch to size and modification time comparison mode instead of hash-only comparison in the job's advanced settings. This reduces false positives from hash incompatibility.