Question
When reviewing the History log in the CrashPlan app, I see a message similar to:
439 files (558.10MB) backed up, 24.50MB encrypted and sent @ 86.2Kbps (Effective rate: 6.1Mbps)Why are these two numbers different, and what do they mean?
Answer
The two numbers differ because of data deduplication. "Backed up" refers to the total size of the files the CrashPlan app analyzed and processed during that backup. "Encrypted and sent" refers to the actual amount of new data that was transferred over your network to the backup destination. If the app recognizes that parts of your files are already stored in the archive archive, it will not upload them again.
Additional info
- Effective Rate vs. Sent Rate: In that same log line, you will likely see two different speed metrics. Your sent rate is your actual network upload speed for the new data. Your effective rate is much higher because the app credits you for the deduplicated data it processed instantly without needing to upload it.
- Common Scenarios: You will frequently see a large discrepancy between these numbers if you recently renamed a large folder, moved files to a new location, or replaced a device. The app will show a large amount of data "backed up," but a very small amount "encrypted and sent" because the data itself hasn't actually changed. See Is my backup starting over? for more details.