Alternate Storage Site

The alternate storage site requirement means you must maintain a separate location where you can store and retrieve system backup information under formal agreements, and that site must meet security controls equivalent to your primary environment (NIST Special Publication 800-53 Revision 5). Operationally, you need a documented design, enforceable third-party terms, validated access paths, and evidence that backups can be restored from the alternate site.

Key takeaways:

• You need both a technical alternate storage capability and enforceable agreements that allow storage and retrieval.
• “Equivalent controls” must be provable, not assumed; map and test controls at the alternate site.
• Auditors look for restore evidence, access control rigor, and contract language, not just architecture diagrams.

“Alternate Storage Site” (NIST SP 800-53 Rev 5 CP-6) is a continuity requirement that often gets implemented as “we have backups in another region” and then fails in an assessment because the operator cannot prove equivalency of controls, retrieval rights, or actual restore capability (NIST Special Publication 800-53 Revision 5). In FedRAMP Moderate contexts, this control is less about storage volume and more about governance: where backups live, who can access them, what happens if a primary site is impaired, and whether you can restore using only the alternate site.

For a Compliance Officer, CCO, or GRC lead, the fastest path is to treat CP-6 as three deliverables: (1) an alternate storage site architecture (including encryption, access, logging, and key management), (2) binding agreements with any third party involved in storing or moving backups, and (3) repeatable evidence from restore testing that proves you can retrieve and use backups from the alternate site under real conditions (NIST Special Publication 800-53 Revision 5). This page turns that into a step-by-step implementation checklist, the artifacts to retain, and the audit questions you’ll get.

Regulatory text

Requirement (CP-6): “Establish an alternate storage site, including necessary agreements to permit the storage and retrieval of system backup information; and ensure that the alternate storage site provides equivalent controls to that of the primary site.” (NIST Special Publication 800-53 Revision 5)

What the operator must do:

1. Establish an alternate storage site for backups (separate from the primary site).
2. Put agreements in place (internal and/or third-party) that explicitly allow storage and retrieval of backup information.
3. Ensure the alternate storage site enforces equivalent security controls to the primary site, and be able to demonstrate that equivalence (NIST Special Publication 800-53 Revision 5).

Plain-English interpretation (what CP-6 really demands)

• You need a second place to store backups that remains available when the primary site is degraded, unavailable, or under incident response constraints.
• You must have legal and operational permission to place backups there and to pull them back out when needed. If a third party provides the storage, your contract must not block retrieval during disputes, outages, or account changes.
• “Equivalent controls” means the alternate site cannot be a weaker environment (for example, different encryption standards, looser admin access, missing logs, or unmanaged keys). If your primary environment is FedRAMP-aligned, the alternate storage arrangement must not silently downgrade security (NIST Special Publication 800-53 Revision 5).

Who it applies to (entity and operational context)

Applies to:

• Cloud Service Providers (CSPs) operating in a FedRAMP Moderate context, where backup storage commonly spans accounts, regions, availability zones, or separate cloud services (NIST Special Publication 800-53 Revision 5).
• Federal Agencies operating information systems that rely on backups and may use third parties for storage, archiving, or managed backup services (NIST Special Publication 800-53 Revision 5).

Operational contexts where CP-6 is examined hardest:

• Backups stored in a different cloud account/tenant or managed by a third party (contract and access questions).
• Cross-region or cross-site storage where keys, IAM, logging, and network paths differ from primary.
• “Cold” backups that have not been restored recently (evidence questions).

What you actually need to do (step-by-step)

Step 1: Define the alternate storage site pattern you will use

Pick a pattern you can defend and operate:

• Separate geographic site/region under the same cloud provider
• Separate cloud account/tenant (recommended for blast-radius reduction)
• Different provider (adds resilience, increases complexity)
• Third-party managed backup vault (adds contract dependencies)

Document the rationale and the boundaries: what data is backed up, where it lands, and what systems depend on restore.

Step 2: Write the “retrieval rights” into agreements

CP-6 explicitly requires “necessary agreements to permit the storage and retrieval” (NIST Special Publication 800-53 Revision 5). If a third party is involved, ensure your contract/SLA/SOW (or equivalent) covers:

• Your right to retrieve backups on demand and during emergencies
• Data ownership and return/destruction terms
• Access methods (API, console, offline export) and support obligations
• Key management responsibilities (who controls encryption keys)
• Logging and audit support (access logs, administrative actions)
• Subcontractor flow-down if the third party uses additional third parties

Practical tip: include an explicit clause that retrieval support remains available during account suspension, disputes, or service transitions, subject to lawful constraints. Auditors will probe whether retrieval depends on “best efforts” support tickets.

Step 3: Map “equivalent controls” from primary to alternate

Build a short control equivalency matrix for backup storage. Keep it evidence-driven:

Control area	Primary site standard	Alternate storage site requirement	Evidence to keep
Encryption at rest	Defined encryption + key control	Same or stronger; no weaker algorithm or unmanaged keys	KMS/Key policy exports, storage encryption settings
Encryption in transit	TLS/mTLS or approved channels	Same transport protections	Network diagrams, config snapshots
Access control	Least privilege, MFA, break-glass	Same roles, same MFA, reviewed access	IAM role list, access reviews
Logging/monitoring	Admin and data access logs	Same log coverage and retention	Log source list, sample events
Integrity	Immutability / write protection	Same protections for backups	Vault lock settings, WORM policies
Segregation	Tenant/account separation	Same separation objective	Account structure diagrams

You are not proving the entire system is identical. You are proving the controls protecting backup information at the alternate site are equivalent to those at the primary site (NIST Special Publication 800-53 Revision 5).

Step 4: Implement the technical controls at the alternate site

Minimum operational outcomes you should be able to demonstrate:

• Backups are replicated or copied to the alternate storage location reliably.
• Only approved identities can write backups; only a narrower set can read/restore backups.
• Backup storage is encrypted, keys are controlled, and key access is logged.
• Backup objects are protected from deletion or tampering consistent with your policy.

Step 5: Prove “storage and retrieval” with restore testing

Auditors frequently reject “we replicate backups” without restore evidence. Create a restore test procedure that:

• Uses backups from the alternate site (not the primary)
• Restores into a controlled environment
• Captures proof: ticket, runbook, logs, timestamps, output validation

Keep the test scoped to representative systems if you have many workloads, but justify the sampling approach.

Step 6: Operationalize ownership and change control

Assign accountable owners:

• Backup platform owner (technical)
• Contract owner (third-party management)
• Control owner (GRC)

Tie changes to:

• onboarding a new system to backup
• changing storage class/vault settings
• key rotation model changes
• third-party contract renewals

If you use Daydream to manage third-party risk and evidence, treat the alternate storage provider like a high-dependency third party: store the contract clauses, control mapping, and restore-test artifacts in one assessment record so renewals and audits do not trigger a scramble.

Required evidence and artifacts to retain

Keep evidence that answers the control in one pass:

• Architecture diagram showing primary backup sources, transfer path, and alternate storage site.
• Backup and restore runbooks (including who can declare restore and who can access backups).
• Agreement artifacts for any third party: contract/SOW/SLA clauses covering storage and retrieval rights (NIST Special Publication 800-53 Revision 5).
• Control equivalency matrix (primary vs alternate) with references to configuration exports.
• Configuration evidence: encryption settings, IAM policies/roles, logging enabled, immutability settings.
• Restore test evidence: test plan, execution record, outcomes, issues found, remediation records.
• Access review records for identities with read/restore permissions.
• Exception register if anything is not equivalent, with compensating controls and approval.

Common exam/audit questions and hangups

Expect questions like:

• “Show me the contract language that guarantees retrieval rights.” (NIST Special Publication 800-53 Revision 5)
• “How do you know the alternate site has equivalent controls? Where is it mapped?”
• “Demonstrate a restore from the alternate site. Not a screenshot of replication status.”
• “Who can decrypt backups at the alternate site? Who can approve that access?”
• “Is the alternate storage separated from the primary administrative boundary, or can a single compromised admin delete both?”

Hangup pattern: teams show a DR region but backups are still administered by the same privileged group with broad delete rights, and immutability is not configured. That undermines the “alternate” premise during ransomware scenarios.

Frequent implementation mistakes (and how to avoid them)

1. Mistake: Treating “alternate site” as “another folder/bucket.”
   Fix: require separation that reduces correlated failure (account/tenant separation, independent admin controls) and document why it qualifies.

2. Mistake: No explicit retrieval rights in third-party agreements.
   Fix: add retrieval SLAs, termination assistance, and clear data ownership/return language (NIST Special Publication 800-53 Revision 5).

3. Mistake: “Equivalent controls” assumed, not evidenced.
   Fix: maintain a control equivalency matrix with config exports and periodic review triggers.

4. Mistake: Replication is healthy, restore is untested.
   Fix: run restore tests from the alternate site, capture artifacts, track findings to closure.

5. Mistake: Same keys and same admins across primary and alternate.
   Fix: separate duties where feasible, narrow restore permissions, and enforce strong logging and approvals.

Enforcement context and risk implications

No public enforcement cases were provided in the available source catalog for this requirement. Practically, CP-6 failures surface as audit findings, authorization delays, and incident impact amplification: if you cannot retrieve clean backups from a protected alternate site, you extend outage time and weaken ransomware recovery options. The business risk is not theoretical; it shows up during real restorations, contract disputes, or account-level compromise.

Practical 30/60/90-day execution plan

First 30 days (Immediate)

• Confirm your alternate storage design and document boundaries.
• Inventory which systems’ backups must be covered.
• Identify all third parties involved in backup storage, transfer, or key management.
• Draft the control equivalency matrix outline and list missing evidence.

Next 60 days (Near-term)

• Update or execute agreements to explicitly permit storage and retrieval (NIST Special Publication 800-53 Revision 5).
• Implement or tighten encryption, IAM least privilege, logging, and immutability at the alternate site.
• Publish restore runbooks and assign named owners for restore approval and execution.
• Centralize artifacts in your GRC system (Daydream can keep contract clauses, evidence, and test results together for audit-ready packages).

By 90 days (Operationalize)

• Run a restore test from the alternate storage site and document outcomes.
• Close gaps found in restore testing (permissions, network paths, keys, tooling).
• Put CP-6 into steady-state: change triggers, periodic access reviews, and evidence refresh cycles aligned to your audit calendar.

Frequently Asked Questions

Does “alternate storage site” require a different cloud provider?

CP-6 requires an alternate storage site with equivalent controls and retrieval agreements; it does not specify a different provider (NIST Special Publication 800-53 Revision 5). A separate region or separate account can qualify if you can defend independence and control equivalency.

If we use a third-party backup tool that stores data in their tenant, what do auditors want to see?

Expect scrutiny on contractual retrieval rights and control equivalency (NIST Special Publication 800-53 Revision 5). Keep the agreement terms, evidence of encryption and access controls, and a restore test that pulls from the third party’s storage.

What counts as “equivalent controls” for the alternate storage site?

Equivalent controls means protections for backup information are not weaker than at the primary site, especially encryption, access control, and logging (NIST Special Publication 800-53 Revision 5). Prove it with a mapping and configuration evidence, not informal statements.

Can the alternate storage site be the same region but a different account?

It can be, if you can show meaningful separation and equivalent controls for the backup data (NIST Special Publication 800-53 Revision 5). Document the threat model and why the separation reduces correlated failure for your environment.

What evidence is most commonly missing in CP-6 audits?

Teams often lack restore test artifacts from the alternate site and contract language that guarantees retrieval (NIST Special Publication 800-53 Revision 5). Build your evidence package around those two items first.

How do we handle “equivalency” if the alternate storage uses a different storage class or technology?

Different technology is acceptable if the security outcomes match: encryption, access restrictions, logging, and integrity protections should be comparable to the primary site (NIST Special Publication 800-53 Revision 5). Capture the differences and show compensating controls where needed.