Why This Topic Matters
Air-gapped backup keeps at least one backup copy logically or physically separated from the production and attack domain.
Key Decision Points
Separate backup-management identities from production.
Limit connection windows and access paths.
Measure recovery time with real tests.
Do not confuse air gap with immutability.
Architecture and operating model
Air gaps restrict reachability from the attack environment. Offline media, network isolation and logical access restrictions provide different protection. Management paths and shared identities can undermine isolation. Include the temporary connection window used for copying in the threat model.
- 1Controlled production copy
- 2Write and verify
- 3Disconnect
- 4Independent restore
Design parameters
- Connection window
- Record when physical or logical separation opens and who controls it.
- Management separation
- Separate backup management and deletion from production identities; a shared administrator weakens separation.
- Recovery unit
- Distinguish file, application, database and full-system recovery. Each has different dependencies and validation methods.
- Copy consistency
- Do not rely solely on job success. Verify consistency through application preparation, log-chain integrity and actual restores.
- Capacity and transfer
- Calculate using daily change, retention, full-copy method and measured throughput. Measure compression and deduplication rather than assuming ratios.
- Independent recovery
- Test access to backup management, keys, catalogs and target infrastructure after losing production.
Worked example
For a weekly offline copy, assign connection, writing, verification, disconnection and storage to an owner. A copy six days old cannot alone satisfy a daily RPO. Combine offline protection with a separately protected, more recent copy.
Troubleshooting
| Observation | Likely cause / distinction | Verification |
|---|---|---|
| Copy exists but can be deleted during attack | Shared identity or an open management channel may bypass isolation. | Verify rejection of backup-management and deletion access from production using a test identity. |
| Backup succeeds but restore fails | Chain, key, catalog or application-consistency problems may be present. | Perform a real restore to a separate target; review product logs with application validation. |
| Transfer misses the target time | Source reads, networking, target writes or many small objects can limit throughput. | Measure speed and latency across all three layers simultaneously, not just link capacity. |
| Capacity grows faster than forecast | Change rate, full copies, lock periods or delayed cleanup may be missing from the estimate. | Compare actual usage and deletion-eligible points by policy. |
Acceptance checks
- Test that production administration cannot reach the disconnected copy and that the media remains readable.
- Restore the chosen recovery point to a clean target and validate business data.
- Compare the observed data-loss window with target RPO.
- Record preparation, transfer, startup and business approval separately.
- Test required recovery access without the production administrator account.
- Test protected copies with controlled deletion attempts and actual restores.
Related concepts
RPO and the actual loss window
RPO is the acceptable duration of data loss after an incident. A backup schedule alone does not prove it: failed jobs or delayed replication to another site can enlarge the window. Compare the incident time with the latest usable, consistent recovery point. If an incident occurs at 14:00 and the verified copy is from 13:20, the observed loss window is 40 minutes. Set targets per application; a file archive and a database receiving continuous orders may have different requirements.
RTO and end-to-end recovery time
RTO specifies how soon a service must become usable after an incident. Downloading a backup or booting a VM accounts for only part of that duration. Record detection, approval, infrastructure preparation, data transfer, application startup and business validation separately. Define exactly what starts and stops the test clock. The same technical restore duration can produce different business interruptions when dependencies or access approvals introduce additional waiting.
Application consistency
A bootable copy does not prove application-data consistency. Operating-system caches, database logs and write ordering across disks or services affect the result. A crash-consistent copy resembles recovery after an unexpected shutdown; an application-consistent copy follows supported application preparation and write coordination. Validate transaction integrity, relationships between records and application behavior after recovery, rather than only counting files. Confirm backup integration, application version and reported errors before assuming that consistency was achieved.
Immutability and deletion authority
Immutable retention restricts modification or deletion for a defined period. An application promise, storage-enforced protection and physical isolation are different controls. Review lock duration, clock handling, administrative privileges and deletion paths together. Whether data is automatically deleted after expiry depends on the product policy. On a controlled test copy, attempt deletion using ordinary and privileged accounts, then verify recovery from the protected copy. Protection against deletion does not replace a readability or restore test.
Retention and capacity
Retention defines which recovery points are kept and for how long. Daily, weekly and monthly points do not represent identical change patterns; full-copy creation and chain dependencies affect physical capacity. Retention decisions combine business requirements, applicable obligations and technical capacity. Longer retention does not automatically provide better recovery: the right point must be discoverable and readable. When changing a policy, test whether existing points are deleted immediately or handled differently by the product.
Encryption and key lifecycle
Encryption makes data difficult to read without its key; access control, deletion protection and backup address different needs. Identify which layer protects data in transit and data at rest. Key generation, protection, rotation and emergency recovery are part of the design. A key needed to restore a backup must not exist only on the server that could be lost in the incident. Test decryption and key-access recovery using a separate administrator in a lab, and keep real keys out of documentation and support messages.
Primary documentation
How This Content Was Prepared
Doz Teknoloji Technical Team
This content is based on the technical evaluation approach used across Doz Teknoloji's enterprise IT practice areas.
Technical criteria + primary sources
The topic was cross-checked against vendor documentation, publications from standards bodies and other relevant official technical sources.
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