Backup Types Explained: Full, Incremental, Differential and Snapshots
Backup type determines how long a backup takes, how much space it uses, and — the part that matters when it counts — how long a restore takes. The exam tests the trade-off between those three. The three main types Type Copies Backup time Restore needs Full Everything Longest 1 set Incremental Changes since the last backup of any type Shortest Full + every incremental Differential Changes since the last full Grows over time Full + latest differential only Worked through a week Full backup Sunday, then daily backups Monday to Friday. With incrementals: each day copies only what changed since yesterday. Monday's backup is small, so is Friday's. To restore after a Friday failure you need Sunday's full plus Monday, Tuesday, Wednesday, Thursday and Friday — six sets, restored in order. If any one is corrupt or missing, everything after it is unusable. With differentials: each day copies everything changed since Sunday. Monday is small, Friday is large, because it inc...