What does HRESULT 0xC038002E (ERROR_VOLMGR_NUMBER_OF_PLEXES_INVALID) mean?

ERROR_VOLMGR_NUMBER_OF_PLEXES_INVALID

Interpret the state transition: volmgr number of plexes invalid

ERROR_VOLMGR_NUMBER_OF_PLEXES_INVALID has unsigned value 0xC038002E. In the volmgr layer, it rejects a specific contract because the volume layout declares an unsupported or internally inconsistent number of plexes. Diagnosis of this result should follow volume plex descriptor, layout type and regeneration state through one controlled state transition.

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.

Diagnosis of this result should begin with the object model and generation current at the failure. A later successful enumeration may describe a replacement object and cannot retroactively validate the rejected request.

Record geometry, identity and ownership

Keep this HRESULT as the primary result if rollback or cleanup reports another code; those later values describe recovery, not the first rejected invariant for it.

Separate validation from capability

1. Capture the API parameters and object map that led to this result; do not begin with cleanup.
2. Build a passing control with the same disks or image copy and preserve volume ID, plex ordinal, plex type, member array, active/inactive state, health status and current regeneration job.
3. Run the narrow transition described here: serialize the exact VM_VOLUME_LAYOUT buffer, validate every count and Size field, and compare it with a layout produced by a known-good management API while diagnosing this result.
4. Compare resulting IDs, counts, health and ownership to prove the caller crossed the result invariant rather than suppressing it.

The distinction from ERROR_VOLMGR_UNEXPECTED_DISK_LAYOUT_CHANGE is operational. The decisive condition is the volume layout declares an unsupported or internally inconsistent number of plexes; log the neighboring code separately so capability, identity and state are not conflated.

Mechanism-specific note

The count field is part of the layout contract rather than an advisory value. Verify it against the number of serialized descriptors and against the minimum geometry required by the selected layout type for it. Check multiplication and addition for overflow before allocating or copying the variable-length buffer, because a correctly sized allocation can still contain a logically impossible count while diagnosing it.

Verification after correction

Rebuild the layout from enumerated objects and checked arithmetic rather than patching one serialized field; validate counts, indices, sizes, alignment and overflow before submission while diagnosing it. The result repair is incomplete until a fresh enumeration and new handle observe the corrected state.

• 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_UNEXPECTED_DISK_LAYOUT_CHANGE occurs 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.

Technical references

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

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