SC-34(1): No Writable Storage

SC-34(1): No Writable Storage is a narrow requirement with big downstream impact: it forces you to prove that certain components cannot retain data across a restart or power on/off event. The control is usually applied to components exposed to higher risk of tampering, sensitive processing, or remote compromise, such as boundary devices, specialized appliances, or dedicated workloads that should not store secrets locally.

For a Compliance Officer, CCO, or GRC lead, the fastest path is to translate the one-line requirement into three operational questions: (1) Which components are in scope, (2) what technical pattern guarantees “no persistent writable storage,” and (3) what evidence convinces an assessor that the pattern is real and continuously maintained. If you do not answer those questions, teams tend to hand-wave with “ephemeral instances” or “we don’t store data there,” then fail at audit time because nobody can demonstrate the behavior on restart, power cycle, or during incident response.

This page gives requirement-level implementation guidance you can hand to engineering: scoping rules, step-by-step execution, an evidence bundle, common audit traps, and a practical rollout plan aligned to how assessors test controls. ¹

Regulatory text

Requirement (verbatim): “Employ [system components] with no writeable storage that is persistent across component restart or power on/off.” ²

Plain-English interpretation

• You must select and configure specific components so they cannot write data to storage that survives a restart or power loss.
• “No writable storage” is about persistence, not whether the component can temporarily hold data in memory.
• If the component has a disk, flash, NVRAM, persistent logs, or a writable partition that remains after reboot, it is usually not compliant unless you can prove writes are non-persistent (for example, tmpfs/ramdisk-only) or the writable media is removed/disabled and cannot be used.

What an operator must do

1. Name the in-scope components (the bracketed “[system components]” is intentionally organization-defined). ²
2. Engineer out persistence on those components (by design, configuration, or managed deployment pattern).
3. Prove it with testable, repeatable evidence tied to assets and configurations.

Who it applies to (entity and operational context)

This control is commonly expected in:

• Federal information systems and contractor systems handling federal data, where NIST SP 800-53 is used for control baselines and assessments. ¹
• Environments where you deploy components that are higher-risk to compromise or tampering, including:
  • Boundary and security appliances (firewall/IDS/IPS/proxies) when configured to be stateless
  • Jump infrastructure and bastion-like components designed to avoid local persistence
  • Kiosk/OT/edge nodes in untrusted locations
  • Disposable compute for sensitive workflows (for example, build runners) where residual data is a concern

GRC scoping note: You are not required to make every component in your enterprise non-persistent. You are required to ensure the specific components you designate for SC-34(1) meet the “no persistent writable storage” property, and that the designation is defensible. ²

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

Step 1: Build a “SC-34(1) component inventory”

Create a list of components where you will enforce no persistent writable storage. For each entry, capture:

• Asset identifier (hostname, instance pattern, appliance model)
• Environment (prod/dev, enclave, boundary zone)
• Function (what it does)
• Owner (engineering team + accountable manager)
• Storage design (what storage exists, what is writable, what persists)

Practical tip: If you cannot clearly explain why a component is in scope, assessors will question whether the control is meaningful or is being applied opportunistically.

Step 2: Choose an implementation pattern that guarantees non-persistence

Use one of these patterns, and document which one you chose per component:

Pattern	What it means in practice	Where it fits	Audit proof focus
Diskless / no local persistent media	No HDD/SSD/flash used for writes that survive restart	Appliances, hardened edge devices	Hardware specs, config showing no writable persistent partitions
Read-only OS + volatile write paths	Root filesystem immutable; writes only to RAM-backed filesystems	Immutable infrastructure, containers, minimal OS nodes	Mount tables, filesystem policy, config management
Ephemeral instances with enforced no-persist	Instances are replaced; any local disk is ephemeral; no durable volumes attached	Cloud autoscaling groups, disposable workers	IaC showing no persistent volumes, restart/power-cycle behavior test
Centralized logging and state	No local logs/state; forwarded off-box; local caching is volatile only	Security gateways, proxies	Logging config, no local retention, restart test

Your goal is to remove “operator intent” from the equation. “We don’t store anything” is not a control. A control is a design constraint that prevents persistence even if someone tries. ¹

Step 3: Implement config guardrails (not just a one-time build)

To operationalize SC-34(1), implement guardrails that prevent drift:

• Infrastructure-as-Code rules: block attachment of persistent volumes to in-scope instance profiles; block enabling local persistent logging paths for those images.
• Configuration baselines: read-only mounts where feasible; volatile directories mapped to RAM; disable swap if it creates persistent artifacts on disk for in-scope components (where applicable to your architecture).
• Gold images / hardened builds: a “SC-34(1) image” that is used only for these components.
• Exception workflow: if engineering needs persistence for a justified reason, route to a formal exception with compensating controls.

Step 4: Test the requirement the way an assessor will

You need a simple, repeatable test that demonstrates: “writes do not persist across restart/power on/off.” Examples of what to test and record:

• Create a file in a purported write path, restart, confirm it is gone.
• Confirm the component cannot mount or access persistent writable partitions.
• Confirm logs are not retained locally after restart if local retention implies persistence.

Record:

• Test date, tester, component ID(s)
• Commands or steps used
• Evidence (screenshots, console output, configuration snapshots)
• Result and remediation ticket if failed

Step 5: Put it on a control cadence with ownership

SC-34(1) breaks when teams change images, add agents, or “temporarily” attach storage for troubleshooting. Make the control live:

• Assign a control owner in Engineering and an oversight owner in GRC.
• Run a recurring control health check tied to change events:
  • New images
  • New instance types
  • New logging/monitoring agents
  • Architecture changes for the in-scope components

Daydream fit (earned mention): If you manage many third parties and internal platform teams, Daydream can store the control card, exception decisions, and the minimal evidence bundle so you can answer customer and assessor questions without rebuilding the story each cycle.

Required evidence and artifacts to retain

Keep an evidence bundle that maps cleanly to the requirement language:

1) Control design artifacts

• SC-34(1) control card: objective, scope, owners, trigger events, execution steps, exception rules
• Architecture diagram or system description showing where in-scope components sit in the environment

2) Asset- and config-level proof

• Inventory of in-scope components with identifiers and owners
• Configuration evidence showing no persistent writable storage, such as:
  • Mount configuration / filesystem policy excerpts
  • IaC snippets showing no persistent volumes attached
  • Image build documentation indicating immutable design

3) Operating effectiveness

• Restart/power-cycle test records and outputs
• Drift/monitoring outputs or periodic attestations from system owners
• Tickets for any failures and closure evidence

4) Exceptions

• Approved exception with:
  • Business justification
  • Scope (which components)
  • Compensating controls
  • Expiration or review trigger
  • Residual risk acceptance sign-off

Common exam/audit questions and hangups

Expect assessors to push on these points:

1. “Which components are ‘system components’ for SC-34(1)?”
   Have your scoped list and rationale ready. अस्प scope without rationale reads like guesswork. ²

2. “Show me that writes cannot persist across restart.”
   Provide your test procedure and the last execution evidence. They will often pick a sample component and ask you to repeat the test.

3. “What about logs, crash dumps, swap, agent caches?”
   If any of those persist on writable media, you need to show they are redirected off-box or are volatile only.

4. “How do you prevent configuration drift?”
   Point to guardrails: IaC policies, baselines, change controls, and periodic checks.

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails	Fix
Declaring “ephemeral compute” without proving storage behavior	Ephemeral instances can still write to persistent volumes or retain data on attached disks	Enforce IaC constraints and run restart tests per pattern
Scoping is vague (“some servers”)	Assessors cannot sample or validate	Maintain a named, owner-assigned inventory
Local logging retained “for troubleshooting”	Local logs are persistent writable storage	Centralize logs; restrict local retention to volatile storage
No exception process	Teams bypass the control under pressure	Require time-bounded exceptions with compensating controls and sign-off
Confusing encryption with non-persistence	Encryption protects confidentiality, not persistence	Keep encryption as a compensating control, not a substitute

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so you should treat SC-34(1) as an assessment and assurance control rather than one tied to specific penalties in this page.

Operational risk is still concrete:

• Persistent writable storage on exposed components increases the chance of data remanence, credential residue, and attacker persistence.
• During incident response, non-persistent designs reduce what can be stolen after-the-fact and simplify rebuild strategies.
• In customer diligence, weak evidence for SC-34(1) usually surfaces as “control exists on paper” because teams cannot demonstrate restart behavior.

A practical 30/60/90-day execution plan

First 30 days (Immediate: scope + design lock)

• Name an owner in Engineering and a control owner in GRC.
• Define the in-scope component categories and build the initial inventory.
• Pick an approved implementation pattern per category (diskless, read-only OS, volatile write paths, enforced ephemeral).
• Draft the control card and exception workflow (who can approve, what evidence is required).

Days 31–60 (Near-term: implement guardrails + first evidence)

• Implement IaC and configuration guardrails to prevent persistent storage attachment or use.
• Build or standardize the “SC-34(1) compliant” images/config profiles.
• Run and document the first round of restart/power-cycle tests for each in-scope group.
• Open remediation items for any component that fails, and track to closure.

Days 61–90 (Ongoing: operationalize and make it auditable)

• Put the health check on a recurring cadence and tie it to change triggers (new image releases, agent installs, infra changes).
• Audit your own evidence bundle: can you answer sampling requests quickly?
• Validate exception hygiene: expired exceptions, missing compensating controls, unclear scope.
• Store the control card, evidence bundle, and exceptions in a system that supports audits and customer requests (Daydream can act as the system of record for control operation and evidence packaging).

Frequently Asked Questions

Does SC-34(1) mean the component can never write anything at all?

It means the component must not have writable storage that persists across restart or power on/off. Temporary writes to memory or volatile filesystems can be acceptable if you can prove nothing persists after restart. ²

Are cloud instances automatically compliant because they are “ephemeral”?

No. A cloud instance can still have persistence through attached volumes, snapshots, retained logs, or writable disks that survive restarts. Treat “ephemeral” as an implementation pattern you must enforce and test. ¹

What evidence is strongest for auditors?

The highest-value evidence is a repeatable test showing data written before restart is absent after restart, plus configuration/IaC proof that persistent writable storage cannot be added without breaking policy. Pair that with a scoped inventory and ownership. ²

What if a component needs a small persistent cache to function?

Treat that as an exception. Document the business need, limit the scope, add compensating controls (for example, hardening, monitoring, encryption as appropriate), and set a review trigger so it does not become permanent by default. ¹

How do we handle third-party managed appliances?

Put the requirement in the third-party security addendum: require a statement of how the appliance avoids persistent writable storage (or which parts persist), plus your right to receive configuration evidence. If the third party cannot meet it, document an exception and compensating controls. ¹

Is centralized logging required for SC-34(1)?

The control text does not mandate centralized logging, but most implementations need it because persistent local logs can violate the “no persistent writable storage” constraint. Central logging is a common compensating design choice to preserve auditability without local persistence. ²

Footnotes

1. NIST SP 800-53 Rev. 5

2. NIST SP 800-53 Rev. 5 OSCAL JSON