윈도우 백업 오류 - a Volume Shadow Copy Service operation failed.

다음과 같은 이벤트 로그와 함께 윈도우 백업이 실패했습니다.

Log Name:      Application
Source:        SPP
Date:          2017-12-06 오전 1:12:50
Event ID:      16387
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      testpc.testad.com
Description:
Writer Microsoft Hyper-V VSS Writer experienced some error during snapshot creation.  More info: .

Log Name:      Application
Source:        Microsoft-Windows-Backup
Date:          2017-12-06 오전 1:14:09
Event ID:      521
Task Category: None
Level:         Error
Keywords:      
User:          SYSTEM
Computer:      testpc.testad.com
Description:
The backup operation that started at '?2017?-?12?-?05T16:01:42.205000000Z' has failed because the Volume Shadow Copy Service operation to create a shadow copy of the volumes being backed up failed with following error code '0x807800A1'. Please review the event details for a solution, and then rerun the backup operation once the issue is resolved.