What does HRESULT 0x400D0056 (NS_I_DISK_REBUILD_STARTED) mean?

NS_I_DISK_REBUILD_STARTED

NS_I_DISK_REBUILD_STARTED — 0x400D0056

Treat this code as a record of content disk rebuild start: in the operation that returned it, the server began reconstructing the legacy content-disk structures identified in the event.

The contract behind the code

Rebuild events form a stateful sequence with one owner, an initial disk condition, reconstruction sources, progress, and a terminal result. In the context of content disk rebuild start, preserve the entire sequence and the pre-rebuild identity data; repeated starts can destroy the evidence that distinguishes source loss from destination failure. Locate the first component that changes state and distinguish later summary errors.

Important distinction. Starting reconstruction does not mean data integrity has been restored; completion or abortion and post-rebuild reads must be examined.

Diagnostic worksheet

• Disk ID, server name, rebuild start time, source peers or surviving stripes, and expected data set
• Free space, I/O error counters, filesystem health, and control-block version before reconstruction
• Rebuild progress events and any concurrent restripe or offline action
• Operator action or automatic condition that initiated the rebuild

Collect enough to identify the attempt without copying private media or secrets; hashes, object IDs, timestamps, and configuration exports are normally sufficient.

Useful comparisons

• Measure whether source data and destination capacity remain stable throughout a small controlled rebuild. Use a disposable publishing point or maintenance window when the test can alter server or storage state.
• Verify that no second administrator or automation task is stopping or restriping the same disk. Retain a known-good stream, session, or server object so a broad restart is not mistaken for repair of the reported failure.
• Compare rebuild duration and I/O errors with a known healthy disk of similar size.

Read the result in context

Also check severity: informational and warning values are observations or policy notifications and should be routed differently from a failure HRESULT even when an event viewer labels the source generically.

A defensible fix

Correction: Remove the underlying media, capacity, peer, or metadata obstacle and allow one rebuild owner to complete the operation.

Accept the repair only when a finished event follows, control metadata is consistent, sample content validates, and no automatic rebuild immediately restarts.

Technical references

These sources describe the API, service architecture, and status values relevant to this diagnosis: Check version-specific behavior against the Windows Media Services and SDK generation that produced the event.

• Microsoft Open Specifications: HRESULT values — defines the formal status.
• Microsoft: Windows Media Services 9 Series SDK — documents the relevant API or lifecycle.
• Microsoft: Windows Media Services SDK architecture — provides the architecture, format, or protocol context.
• Microsoft: programming the Windows Media server object model — supports the controlled verification criteria.