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ERROR_VOLMGR_MEMBER_INDEX_DUPLICATE
What this result says about the disk model: volmgr member index duplicate
The practical meaning of ERROR_VOLMGR_MEMBER_INDEX_DUPLICATE (0xC0380024) is tied to dynamic-volume plex member descriptor and its backing extents: the submitted layout names the same member position more than once, making the plex definition ambiguous. The result does not, by itself, prove file-system corruption or physical-media failure.
Dynamic volumes are represented as packs containing disks and volumes; each volume has one or more plexes, and each plex is assembled from members and extents. Indices and counts are relative to the submitted layout generation, while configuration logs are replicated across participating dynamic disks. This object model determines which identifiers, counts and ownership state are meaningful while diagnosing this result.
The standard message identifies the immediate condition, but this result also requires the producer API, object topology and attempted state transition while diagnosing it. Capture them before an automatic refresh advances the storage generation.
Capture the exact object generation
| Storage diagnostic field | Value |
|---|---|
| Closest comparison | ERROR_VOLMGR_MEMBER_INDEX_INVALID |
| Owning object | dynamic-volume plex member descriptor and its backing extents |
| Rejected invariant | the submitted layout names the same member position more than once, making the plex definition ambiguous |
| Identity and generation | pack ID, volume ID, plex index, member index, disk IDs, extent offsets, health state and regeneration percentage |
| Narrow experiment | submit a copied layout with one deliberately repeated ordinal, then change only that ordinal to a unique value |
Do not overwrite this result with a close, detach or rollback error. Preserve the causal order so the original storage contract remains visible for it.
Prove the boundary in a test volume
- serialize the failing request and the enumeration from which its identifiers came while diagnosing this result.
- Preserve pack ID, volume ID, plex index, member index, disk IDs, extent offsets, health state and regeneration percentage while every handle is still valid.
- Repeat the operation using this controlled change: submit a copied layout with one deliberately repeated ordinal, then change only that ordinal to a unique value.
- Close and reacquire the relevant objects, then run once more to test lifecycle correctness after it.
Compare traces for ERROR_VOLMGR_MEMBER_INDEX_INVALID and it. The latter page covers a nearby storage boundary, whereas it rejects the submitted layout names the same member position more than once, making the plex definition ambiguous. A correct caller should be able to reproduce each case independently.
Mechanism-specific note
This code is about uniqueness inside one serialized array, not about the physical health of the indexed object while diagnosing it. Dump the full ordinal sequence in submission order and identify which two descriptors claim the same slot. Renumbering after filtering or sorting is a common source of this defect because references retained from the prefiltered layout no longer match the emitted array.
Safe recovery path
Rebuild the layout from enumerated objects and checked arithmetic rather than patching one serialized field; validate counts, indices, sizes, alignment and overflow before submission. Apply the change through the supported storage API, then close and reacquire affected objects before retrying.
- The controlled A/B case changes only the invariant responsible for it.
- No unrelated disk, cluster owner, tier policy or virtual-disk backing file is altered to hide it.
- Health, synchronization or job state reaches a terminal value consistent with the repaired the operation.
- Telemetry includes both symbolic names when it or
ERROR_VOLMGR_MEMBER_INDEX_INVALIDoccurs again.
Before responding to it with destructive cleanup, prove which object owns the failure. Changing every disk or provider at once prevents a meaningful regression test while diagnosing it.
Technical references
- Microsoft: COM error codes for VOLMGR, VHD and SDIAG — use this source to verify volmgr state and parameters for it.
- Microsoft: Virtual Disk Service object model — documents the supported management path relevant to it.
- Microsoft: Pack object — defines the volmgr objects used to interpret it.
- Microsoft: Virtual Disk Service common return codes — primary API or object-model reference for the boundary.
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