When Differential Backups Grow Larger Than Fulls

Kenneth Fisher notes that differential backups can end up being larger than full backups of the same database:

The thing about DBA Myths is that they are generally widespread and widely believed. At least I believed this one until I posted What’s a differential Backup?and Randolph West (b/t) pointed out that my belief that differential backups can’t get larger than full backups was incorrect. In fact, differential backups (like FULL backups) contain enough transaction log information to cover transactions that occur while the backup is taking place. So if the amount of data that needs to be backed up combined with transactions requires more space than just the data ….

Read on for a demonstration.

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