Policy
Control mounting ReFS volumes on USB and IEEE 1394 disks
Microsoft Windows
Policy overview
Key metadata and intent for this policy.
Supported OS tags: Windows11
Controls whether ReFS volumes are allowed to mount on disks attached by USB or IEEE 1394. ReFS is not a supported configuration on hot-pluggable or removable disks. Block refuses the mount and records an event in the System log. Audit only allows the mount and records the same event, so the effect of enabling this policy can be assessed before it is enforced. Off performs no auditing and no blocking. For a Storage Spaces volume the check applies to the physical disks backing the pool, not to the space itself. If this policy setting is not configured, the local setting on this computer is used. If no local setting exists, the default behavior for this version of Windows is used. ReFS reads this setting when it loads, so a restart is required before a change applies. The setting is then evaluated each time a volume mounts, so a volume that is already mounted keeps its current state until it is dismounted and mounted again.
Registry values
How enabled and disabled states update the registry.
No explicit registry values are set for enabled or disabled states.
Policy elements
Inputs and configuration options exposed by this policy.
| Scope | Element | Type | Registry mapping | Constraints & behavior | Copy |
|---|---|---|---|---|---|
| Computer | Action for ReFS volumes on USB or IEEE 1394 disks ID BlockExternalBusMountMode | enum | Path System\CurrentControlSet\Policies Value name RefsExternalBusMountPolicy Type REG_DWORD | Options: Off (0), Audit only (1), Block (2) |