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VDS_E_VD_ALREADY_ATTACHED
Attach is a topology operation that surfaces a virtual disk to the operating system. This HRESULT means that topology already exists; another VDS attach request is not required. The state model distinguishes an attached disk with no open virtual-disk file handle from an attached disk that is also open, but both are already attached for this purpose.
Why this state matters
Treating attach as blindly idempotent can hide configuration differences. The existing attachment might have been created with read-only or no-drive-letter flags, or by another client. The correct response is to inspect the current attachment and decide whether it satisfies the caller rather than repeatedly calling Attach.
Diagnostic focus
- Query the virtual-disk state and associated Windows disk device before deciding that a new attach is needed.
- Check whether the existing attachment is read-only and whether volume drive-letter behavior matches the requested policy.
- Identify the component that established the attachment when lifecycle ownership is important to later detach operations.
- If different attach semantics are required, coordinate a safe detach and then perform a new open/attach sequence.
Technical references
IVdsOpenVDisk::Attach · attach vdisk command · VDS_VDISK_STATE · MS-VDS virtual disk state transitions · VDS_VDISK_PROPERTIES
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