HRESULT 0x803100A5: meaning and diagnosis

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Description:

BitLocker Drive Encryption only supports Used Space Only encryption on thin provisioned storage.

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FVE_E_POLICY_PASSPHRASE_REQUIRES_ASCII	FVE_E_WIPE_NOT_ALLOWED_ON_TP_STORAGE

FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE

Read this as a state-machine result

FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE is a BitLocker facility HRESULT, not a Win32 filesystem error wrapped by an application. In this case full-volume encryption was requested on thin-provisioned storage, where BitLocker permits only Used Space Only conversion.

For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, note: Cluster Shared Volumes and thin-provisioned storage add ownership and allocation semantics that a standalone disk does not have. When diagnosing FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, remember: BitLocker operations must respect the CSV coordinator and must not force thin backing storage to allocate every virtual extent.

What the code does not prove

The closest misleading interpretation is a small or nearly full volume; the restriction prevents allocation expansion of thin backing storage. For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, verify the returning method and state transition before assigning the incident to disk corruption, TPM failure or bad credentials.

Inspect the target, not just the message

For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, record provisioning type, virtual disk/VHD mode, conversion method, allocated versus virtual size and storage-pool capacity. For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, keep the full HRESULT and the first method that returned it because later cleanup calls can report a different state.
For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, capture manage-bde -status and the protector inventory for the exact volume GUID, not only the drive letter, because letters can change in WinRE, clusters and deployment environments.
Export BitLocker operational events for the FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE failure and note the boot session, caller identity and management source; that evidence separates this BitLocker condition from a generic access or storage error.

For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, note: Cluster maintenance should preserve resource ownership, quorum assumptions and application shutdown ordering. When diagnosing FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, remember: BitLocker is only one participant in that workflow.

A low-risk recovery path

For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, use Used Space Only encryption and monitor backing allocation; do not force a full sweep that defeats thin provisioning.
After correcting the FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE prerequisite, refresh protection, conversion and lock state before one controlled retry; a cached UI message is not proof that the FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE condition is still active.
Before a FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE remediation deletes protectors, changes firmware mode, resizes partitions or decrypts a production drive, verify that an independent recovery method is available and escrowed in the intended directory or account.

Get-ClusterSharedVolume | Format-List *
manage-bde -status

Result interpretation for FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE

After correction, compare the new conversion, protection and lock state with the original snapshot. A different HRESULT after FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE is useful because it means the request crossed this boundary and reached the next prerequisite.

State checks specific to FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE

Checkpoint	How to interpret it for FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE
Before the call	Record the target identity and the pre-call cluster or thin-storage coordination state. For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, the decisive boundary is that full-volume encryption was requested on thin-provisioned storage, where BitLocker permits only Used Space Only conversion.
At failure	Preserve provisioning type, virtual disk/VHD mode, conversion method, allocated versus virtual size and storage-pool capacity. This proves whether FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE came from BitLocker itself or from a wrapper translating another result.
After correction	Use Used Space Only encryption and monitor backing allocation; do not force a full sweep that defeats thin provisioning. The FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE request should then advance without removing an unrelated recovery route.
After reboot or remount	Recheck protection, conversion and lock state for FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE; a successful management call is incomplete if the next boot cannot unlock the volume.

Verification after the change

For FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE, success means more than the absence of a dialog. Confirm that the condition represented by FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE now matches the intended design, that the protector inventory has not lost an independent recovery route, and that the next reboot or remount can unlock the volume. If the FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE request advances to another HRESULT, record both values in order because that transition reveals the next unmet prerequisite.

References

Reference set for FVE_E_FULL_ENCRYPTION_NOT_ALLOWED_ON_TP_STORAGE:

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