A backup method that backs up all data changed since the previous full backup. Each backup grows as the days since the full backup increase, but a restore needs only two: the full backup and the latest differential backup.
Japanese name: 差分バックアップ
Differential backup appears in 3 practice questions across 1 topic, including System Architecture and Reliability.
A full backup copies all data regardless of whether it has changed. A differential backup copies all changes since the previous full backup, and an incremental backup copies only the changes since the previous backup, whether full or incremental. Generally, full backups are taken at intervals such as once a week, and the time in between is covered by differential or incremental backups.
If a full backup is taken on Sunday and a backup every night from Monday, returning on Friday to the state of Thursday night requires restoring two backups with differential backups: the full backup and Thursday's differential backup. With incremental backups, the full backup is restored and then the four incremental backups from Monday to Thursday are applied in order, so five are needed in total. If even one in the chain is damaged, later points in time cannot be restored.
If 20 GB of different data changes each day, differential backups grow day by day to 20 GB, 40 GB, 60 GB and so on, while incremental backups stay at 20 GB each time. In other words, differential backups take more time and storage but make restores simpler and faster, and incremental backups are the opposite. The choice depends on the time and capacity available for backups and the allowed recovery time (RTO).
Answer: C. Backing up all data changed since the previous full backup
A differential backup backs up all data changed since the previous full backup. Each backup grows as the days since the full backup increase, but a restore needs only two: the full backup and the latest differential backup. Backing up only the changes since the previous backup is an incremental backup; each one is small, but a restore needs the full backup and every incremental backup after it.
Answer: B. 420 GB
A differential backup contains all changes since Sunday's full backup, so each one grows: 20 GB on Monday, 40 GB on Tuesday, and so on, reaching 120 GB on Saturday. The total is 20 + 40 + 60 + 80 + 100 + 120 = 420 GB. With incremental backups each would be 20 GB, for a total of 120 GB, but a restore would need many backups applied in order. Taking a full backup every day would give 6 × 500 = 3,000 GB.
Differential backups suit those who want fast, simple restores, and incremental backups suit those who want to minimize the time and capacity of each backup. Both assume that full backups are taken again regularly.
If backups are kept only on the same server or disk, they are lost together with the original data through a failure of that equipment, ransomware or a fire. Generally, keeping three or more copies, on two or more types of media, with one stored at another location (the 3-2-1 rule) is recommended.
A differential backup backs up all data changed since the previous full backup.
Which describes a differential backup?A differential backup contains all changes since Sunday's full backup, so each one grows: 20 GB on Monday, 40 GB on Tuesday, and so on, reaching 120 GB on Saturday.
In a system with 500 GB of data in total, a full backup is …Two would be enough if differential backups were taken every night (the full backup and Wednesday's differential backup).
A full backup is taken every Sunday night, and an increment…As an Amazon Associate I earn from qualifying purchases.
Incremental backup Dual system Duplex system Fail-safe Fail-soft Fault tolerance Fool-proof Hot standby Load balancer RAID