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VDS_E_DISK_IS_OFFLINE
An offline disk can still have its layout read, but Windows does not surface volume devices for it through Plug and Play. The SAN policy documentation explicitly distinguishes offline disk metadata visibility from online volume-device installation. This HRESULT therefore represents an operation precondition: the requested action requires an online disk object.
Why this state matters
Before bringing the disk online, inspect VDS_DISK_PROP2.OfflineReason and the current SAN policy. Shared storage can intentionally remain offline to prevent simultaneous access. A blind Online retry may be unsafe in clustered or SAN environments. For dynamic disks that are also read-only, Microsoft documents an ordering requirement: clear the read-only attribute before calling Online.
Diagnostic focus
- Record the disk status, offline reason, SAN policy, and read-only/current-read-only flags.
- Confirm that the disk is intended to be owned and accessed by this Windows instance before bringing shared storage online.
- For a dynamic read-only offline disk, clear the VDS read-only attribute before calling
Online. - After the online transition, refresh disk and volume properties before continuing the original operation.
Technical references
VDS_SAN_POLICY · VDS_DISK_PROP2 · VDS_DISK_FLAG · IVdsDiskOnline::Online · IVdsService::Refresh
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