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ERROR_VOLMGR_STRUCTURE_SIZE_INVALID
What this result says about the disk model: volmgr structure size invalid
The practical meaning of ERROR_VOLMGR_STRUCTURE_SIZE_INVALID (0xC0380041) is tied to kernel volume-manager layout transaction and VM_VOLUME_LAYOUT input: one or more Size fields do not match the version and extent counts encoded in the VM_VOLUME_LAYOUT buffer. 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.
A useful record contains more than the final UI symptom: retain the first failing call, target identity, topology and state transition before management software rescans the disks.
Capture the exact object generation
| Storage diagnostic field | Value |
|---|---|
| Narrow experiment | 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 |
| Closest comparison | ERROR_VOLMGR_UNEXPECTED_DISK_LAYOUT_CHANGE |
| Owning object | kernel volume-manager layout transaction and VM_VOLUME_LAYOUT input |
| Rejected invariant | one or more Size fields do not match the version and extent counts encoded in the VM_VOLUME_LAYOUT buffer |
| Identity and generation | pack and volume IDs, input structure version and sizes, transaction ID, disk-layout snapshot before the call and the first kernel storage event |
When it is followed by a secondary cleanup failure, store both codes with timestamps and retain this one as the initiating result for this HRESULT.
Prove the boundary in a test volume
- Capture the API parameters and object map that led to this result; do not begin with cleanup.
- Build a passing control with the same disks or image copy and preserve pack and volume IDs, input structure version and sizes, transaction ID, disk-layout snapshot before the call and the first kernel storage event.
- 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.
- Compare resulting IDs, counts, health and ownership to prove the caller crossed the result invariant rather than suppressing it.
A useful diagnostic fork is ERROR_VOLMGR_UNEXPECTED_DISK_LAYOUT_CHANGE versus this result. This code concerns one or more Size fields do not match the version and extent counts encoded in the VM_VOLUME_LAYOUT buffer; the alternate code should remain observable after the fix, proving the application did not suppress the entire subsystem while diagnosing it.
Mechanism-specific note
VM_VOLUME_LAYOUT is versioned through explicit Size fields and nested variable-length arrays. Capture the compiler architecture, structure version and byte offsets used by the caller. A packing mismatch, stale SDK declaration or count-derived allocation error can make every semantic field look plausible while the kernel rejects the buffer before examining the intended operation while diagnosing this result.
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. Keep the correction scoped to the owning object and avoid rewriting adjacent metadata merely to make the call return success.
- The controlled A/B case changes only the invariant responsible for this HRESULT.
- No unrelated disk, cluster owner, tier policy or virtual-disk backing file is altered to hide this result.
- 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_CHANGEoccurs again.
A reboot, blanket disk conversion or deletion of storage metadata is not a justified first response to it; it changes multiple invariants and can erase the evidence needed to identify the defect while diagnosing it.
Technical references
- Microsoft: COM error codes for VOLMGR, VHD and SDIAG — use this source to verify volmgr state and parameters for this HRESULT.
- 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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