Backup and recovery
CIE A-Level Computer ScienceΒ· Unit 6: Security, privacy and data integrityΒ· 15 min read
1. 1. Purpose of Backupsβ β ββββ± 3 min
Backup
A duplicate copy of current organizational or personal data, stored separately from the original production data, created to restore data after an incident that causes data loss or corruption.
Example:
A retail store backing up daily transaction data to an off-site server.
Backups protect against multiple common causes of data loss, including human error (accidental deletion), hardware failure (hard drive crashes), malware (ransomware encryption), and physical disasters (fire, flood destroying on-site hardware).
Maintain business continuity after data loss: prevents extended downtime that causes revenue loss
Preserve data integrity by allowing restoration to a known uncorrupted state
Comply with legal and regulatory requirements for data retention
Protect against irreversible damage from ransomware attacks
A small business asks why they need a backup if they already store all data on Google Drive. What is the core reason?
- 1
Recognize that cloud storage is primary storage, not a backup.
- 2
Cloud storage only hosts one copy of active data. If data is accidentally deleted or corrupted, the change syncs across all connected devices, leaving no intact copy to recover.
- 3
A separate independent backup stores a copy of data from before the corruption or deletion occurred, enabling recovery.
- 4
A separate backup is required to recover data lost or corrupted in the primary cloud storage.
Exam tip:
In scenario questions, always link your recommended backup strategy to the specific risks described in the question.
2. 2. Common Backup Typesβ β β βββ± 5 min
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Backups are categorized by how much data they copy each time they run. The three core types tested in CIE 9618 are full, incremental, and differential backups.
Backup Type | What it copies | Backup speed | Storage size | Recovery speed |
|---|---|---|---|---|
Full | All selected data | Slow | Large | Fast (1 file needed) |
Incremental | Changes since last backup (any type) | Very fast | Small | Slow (needs all backups since last full) |
Differential | All changes since last full backup | Moderate (grows over time) | Moderate (grows over time) | Fast (only needs full + last differential) |
An organisation runs a full backup every Sunday, and incremental backups every other weekday. If data is lost on Thursday, how many backup files are needed for full recovery?
- 1
Recall that incremental backups only store changes since the last backup of any type.
- 2
Start with the base full backup from Sunday (1 file)
- 3
Add the incremental backup from Monday (changes since Sunday, 2nd file)
- 4
Add the incremental backup from Tuesday (changes since Monday, 3rd file)
- 5
Add the incremental backup from Wednesday (changes since Tuesday, 4th file)
- 6
Total of 4 backup files are required for full recovery.
3. 3. Backup Storage & Disaster Recoveryβ β β βββ± 4 min
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How and where you store backups is just as critical as the backup type for their effectiveness. Storage location is split into on-site and off-site, each with different use cases.
Disaster Recovery Plan (DRP)
A documented set of procedures to recover critical data and IT systems after a major disruptive incident, such as a natural disaster, large-scale cyberattack, or infrastructure failure.
Example:
A hospital's DRP that requires full patient record recovery within 4 hours of a server outage.
On-site backups are stored at the same location as the original data, enabling fast access for quick recovery from common issues like accidental deletion. However, they are vulnerable to site-wide disasters that destroy all on-site infrastructure. Off-site backups are stored at a geographically separate location, protecting against site-wide disasters, with cloud backup being a common modern option.
A small local law firm wants to protect client data against both accidental deletion and a fire that destroys their office. Recommend an appropriate backup storage strategy.
- 1
Address the first risk (accidental deletion): on-site backups allow fast recovery for small, common incidents.
- 2
Address the second risk (office fire): an on-site backup will be destroyed along with the original data, so a separate off-site backup is required.
- 3
Final recommendation: Combine daily incremental on-site backups for quick small-scale recovery, with a weekly encrypted full backup stored on an off-site cloud service. This balances speed for small incidents and protection against large disasters.
4. 4. The Backup Recovery Processβ β ββββ± 3 min
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Recovery is the process of restoring data from backups after loss or corruption. The exact steps depend on the backup type used, but follow a standard general workflow:
Identify the cause of data loss and confirm the point in time to restore to
Verify the integrity of backup files to ensure they are uncorrupted
Restore the base full backup to the target system
Apply any subsequent incremental or differential backups in order
Verify the restored data and bring the system back online
Describe the recovery process for data lost on Thursday, when a full backup is taken every Sunday and a differential backup every Wednesday.
- 1
Confirm the restore point: after Wednesday's changes, before Thursday's data loss
- 2
First restore the full base backup from Sunday to the target system
- 3
Apply the most recent differential backup from Wednesday, which contains all changes made since Sunday
- 4
Verify the restored data is complete and uncorrupted, then bring the system back online
- 5
Only 2 backup files are needed for full recovery, compared to 4 for incremental backups in the same scenario
5. Common Pitfalls
Wrong move:
Confusing incremental and differential backups: stating incremental stores changes since the last full backup
Why:
This mixes up the two types, leading to wrong answers for recovery file count questions
Correct move:
Incremental = changes since any last backup, differential = changes since last full backup
Wrong move:
Assuming primary cloud storage is a complete backup solution
Why:
Cloud storage only stores one copy of active data, so corrupted/deleted data is synced across all devices
Correct move:
Always recommend a separate independent backup even for cloud-hosted primary data
Wrong move:
Storing all backups on-site for disaster protection
Why:
A site-wide disaster like fire or flood will destroy both original and backup data
Correct move:
Always use a geographically separate off-site backup for disaster protection
Wrong move:
Forgetting to verify backup or restored data integrity
Why:
Backups can become corrupted just like primary data, so an unverified backup cannot be trusted
Correct move:
Always include verification of backup integrity before storage and restored data after recovery
Wrong move:
Claiming archives are the same as backups
Why:
Archives serve a different purpose than backups for data protection
Correct move:
Backups are for active recovery of current data; archives are for long-term retention of inactive data
6. Quick Reference Cheatsheet
Property | Full Backup | Incremental | Differential |
|---|---|---|---|
What it copies | All selected data | Changes since last backup | Changes since last full |
Backup speed | Slow | Fastest | Moderate |
Total storage size | Largest | Smallest | Grows over time |
Recovery speed | Fastest | Slowest | Fast |
Files needed (full Sun, backups Mon-Wed, loss Thu) | 1 | 4 | 2 |
7. Frequently Asked
What is the key difference between incremental and differential backup?
Incremental backups store only changes since the last backup of any type, so they are small and fast to create, but recovery requires all incremental backups since the last full. Differential backups store all changes since the last full backup, so they grow over time, but recovery only needs the last full and last differential.
Are backups the same as data archives?
No. Archives store inactive data for long-term regulatory retention, while backups store copies of active data for quick recovery after loss or corruption.
When this came up on past exams
AI-estimated based on syllabus patterns β cross-check with official past papers for accuracy. Use only as revision-focus signals.
- 2022 Β· 1
Differentiate backup types
- 2023 Β· 2
Recommend backup strategy
Going deeper
What's Next
Backup and recovery is a core component of data integrity and organizational cyber security, regularly tested in both paper 1 multiple choice and paper 2 scenario-based questions for CIE 9618. Mastery of this topic supports understanding of larger concepts like disaster recovery and business continuity, which are often paired with other security topics in exams. This topic also links closely to legal compliance requirements for data retention, and to understanding how organizations mitigate common cyber security threats.