A timeout (30000 milliseconds) was reached while waiting for a transaction response from the VSS service.

When I perform "vshadow -ap d: f: e: h:" displays an error text: VSS_E_MISSING_DISK
Returned HRESULT = 0x800423f8

In Windows Logs, There are two error:
1、Event 12362,VSS
   An expected hidden volume arrival did not complete because this LUN was not detected.
    LUN ID   {1ad243aa-d6d9-4537-82f6-a1e2884e1b7a}
    Bus Type  0x0000000000000009
    Version  16
    Identifier Count 1
 Identifier  0
 CodeSet  "VDSStorageIdCodeSetBinary" (1)
 Type  "VDSStorageIdTypeFCPHName" (3)
 Byte Count 16
 
   Operation:
   Exposing Volumes
   Locating shadow-copy LUNs
   PostSnapshot Event
   Executing Asynchronous Operation

Context:
   Current State: DoSnapshotSet

2、Event 7011,Service Control Manager
   A timeout (30000 milliseconds) was reached while waiting for a transaction response from the VSS service.

question: 1、What is A timeout（30000 milliseconds) means？From which interface to which the interface?
          2、What a scene to be wrong about "Event 12362"?