You want to prevent audit logs from being written to a specific device if the disk is full. What happens to Vault?
When a configured audit device fails, Vault blocks all client requests rather than continuing without logging, preventing unlogged operations. This satisfies the scenario's constraint by halting request processing instead of silently dropping audit records to the full device.
Why this answer
If an audit device's disk is full and Vault cannot write audit logs, Vault enters a blocked state and rejects all client requests. This is the same fail-closed behavior as any audit_failure: Vault refuses to process operations it cannot audit. It does not silently drop logs or rotate them automatically.
Exam trap
The trap is thinking Vault will self-heal (rotate, failover, or drop logs) when audit storage fills — candidates miss that Vault blocks all requests instead.
How to eliminate wrong answers
Option B is wrong because Vault does not automatically switch to a secondary file or device on disk-full — it blocks. Option C is wrong because Vault does not continue operating without logging; that would defeat the audit guarantee. Option D is wrong because Vault does not delete old logs to free space; log rotation is an operator responsibility, not automatic Vault behavior.