What does HRESULT 0xC0380026 (ERROR_VOLMGR_MEMBER_MISSING) mean?

ERROR_VOLMGR_MEMBER_MISSING

Identify the owner before touching the layout: volmgr member missing

ERROR_VOLMGR_MEMBER_MISSING (0xC0380026) is emitted by the volmgr path when the layout references a plex member whose backing disk extent is absent from the current pack. The deciding object is dynamic-volume plex member descriptor and its backing extents, so the first investigation belongs there rather than in a generic “disk failure” bucket.

Minimum diagnostic set

A management layer handling this result should report later recovery errors separately, because they answer a different question from the failed storage operation.

Reproduce without destructive cleanup

1. Create a nonproduction case that preserves the same geometry and ownership model.
2. Collect pack ID, volume ID, plex index, member index, disk IDs, extent offsets, health state and regeneration percentage before invoking the first mutating API.
3. Change one condition only: capture the disk/extent inventory, re-present the missing test disk without changing IDs, and repeat the lookup or repair request.
4. Re-enumerate after the transition and confirm it is not reproduced by a stale handle from the old generation.

A useful diagnostic fork is ERROR_VOLMGR_MEMBER_NOT_DETACHED versus it. This code concerns the layout references a plex member whose backing disk extent is absent from the current pack; the alternate code should remain observable after the fix, proving the application did not suppress the entire subsystem.

Mechanism-specific note

“Missing” is an identity result: metadata names an object whose backing extents are not present in the current pack view. Compare disk unique IDs and extent offsets rather than substituting a same-sized disk. If the original disk returns, re-enumerate before repair so the recovered object is matched to its existing metadata instead of added as a new member.

Restore the contract

Restore access to the identified disk or extent and confirm its identity and health; do not substitute a different disk merely because its size matches. The repair is incomplete until a fresh enumeration and new handle observe the corrected state.

• the first retry uses newly enumerated identifiers rather than cached handles.
• The durable metadata or provider state agrees with the success returned after it.
• A second run after close/reopen does not recreate the rejected condition.
• the nearby ERROR_VOLMGR_MEMBER_NOT_DETACHED path remains separately testable and separately logged.

Technical references

• Microsoft: COM error codes for VOLMGR, VHD and SDIAG — defines the volmgr objects used to interpret it.
• Microsoft: Virtual Disk Service object model — primary API or object-model reference.
• Microsoft: Pack object — use this source to verify volmgr state and parameters.
• Microsoft: Virtual Disk Service common return codes — documents the supported management path relevant to this HRESULT.