What does HRESULT 0xC05CFF05 (ERROR_SVHDX_UNIT_ATTENTION_REGISTRATIONS_PREEMPTED) mean?

ERROR_SVHDX_UNIT_ATTENTION_REGISTRATIONS_PREEMPTED

Registration membership changed

ERROR_SVHDX_UNIT_ATTENTION_REGISTRATIONS_PREEMPTED indicates that this initiator’s persistent-registration state was preempted. A registration is the membership record represented by a reservation key; it is not automatically the same thing as being the current reservation holder. Removing or replacing a registration changes which initiators are eligible to participate in the shared-storage access policy.

This distinction matters in clustered storage. A maintenance or fencing operation can remove a failed member’s registration to prevent it from reclaiming access. A stale guest or a node with an incorrect key can then see this Unit Attention even if it has not issued the command that changed the state. The meaningful question is not merely whether I/O can be retried, but whether this initiator is still an authorized member of the storage-consumer set.

Diagnostic sequence

• Record the initiator identity and reservation key that the workload believed it owned before the event.
• Read the current Persistent Reservation full status to determine whether the registration is absent, replaced, or present with a different relationship to the reservation holder.
• Review cluster membership, fencing history, and any preempt or preempt-and-abort operation around the same time.
• Do not reuse a stale key blindly. Re-registration must follow the service or cluster protocol so that a partitioned or former owner cannot rejoin incorrectly.

Related conditions

If the access grant itself was displaced, the more specific status is ERROR_SVHDX_UNIT_ATTENTION_RESERVATIONS_PREEMPTED. If the initiator simply attempts an unauthorized command under the current state, it can receive ERROR_SVHDX_RESERVATION_CONFLICT. Those outcomes describe different points in the Persistent Reservation lifecycle.

References

• sg3_utils: registration, reservation, preempt, and full-status queries
• Linux kernel documentation: registration behavior for SCSI PR
• Microsoft Open Specifications: Remote Shared Virtual Disk Protocol

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