How Burn by Zaweba checks every file on backup discs
Burn by Zaweba fingerprints each file before burning, reads every disc back and lists each file as passed or failed, so you know your backup is good.
A backup disc that looks fine in Explorer can still hold a file that won't open. The only way to know is to read the disc back and compare. In a backup made with Burn by Zaweba, every file on every disc gets exactly that treatment, and you see the result file by file.
This article is about what that check looks like during a backup and what to do with its results.
Fingerprints before burning
The check starts before anything is written. Burn takes a SHA-256 fingerprint of each file in the backup. When a large file has been split into pieces to fit across discs, each piece gets its own fingerprint too.
Taking the fingerprint first matters. It records what your files were at the moment of the backup, so the comparison afterwards is against the real source rather than against whatever the disc happens to contain.
Reading every disc back
After a disc is burned, Burn reads back every file on it and compares each one with its fingerprint. On a backup of several discs, this happens for every disc, not just the last. The result is a list of each file marked as passed or failed.
That list is what makes the check useful. A simple yes or no for the whole disc tells you something went wrong. A file by file list tells you exactly what, which helps you judge whether the problem is a bad blank, a drive struggling, or something else.
When a disc fails
A disc that fails can be burned again. Do it straight away, with a fresh blank, while the files and the plan are still in front of you. If a second blank fails in the same way, try discs from a different pack, or check the writer in Tools, Drive information, before carrying on.
Don't keep a failed disc in the set on the hope that the bad file doesn't matter. The disc's index describes the whole backup, and you want every disc in the set to be one you can trust.
The setting behind it
The check is on by default. It is controlled by the setting Check every disc after burning, in Settings. Turning it off makes a backup a few minutes faster per disc, but you give up the one moment when a fault is cheap to fix. For backups, leave it on.
The same fingerprints have a second life. When you restore, Burn checks every restored file against them, so the protection follows the files all the way back to your PC. The Backup log also records whether the check passed for each run, which gives you a history to look back on.
Getting the most from the check
Let the reading finish before ejecting a disc. The check needs to read every file, and pulling a disc out early leaves you without a result.
Read the list rather than just the summary when something fails. If only one file failed, note which; if many did, suspect the blank or the drive.
Keep your discs in good order after the check. A disc that passed today is only as good as how it is stored, so file it in a sleeve with its label and keep it out of sunlight.
How it fits with the rest
The backup check is part of the Backup Assistant, and it uses the same SHA-256 fingerprints that Burn records for images and other jobs. If you want to check a disc that wasn't made as a backup, Tools has a separate Verify a disc tool. For backups, though, the check is built in, and with Burn by Zaweba it happens unless you choose otherwise.
