客戶問題概括:
客戶在2008R2 Hyper-V 主機上用自帶Windows Server Backup 備份時出現錯誤無法備份，在Hyper-V主機上發現如下日誌.
Log Name: Microsoft-Windows-Backup
Source: Microsoft-Windows-Backup
Date: 2/5/2015 00:00:22 AM
Event ID: 9
Task Category: None
Level: Error
Keywords:
User: SYSTEM
Computer: HV01
Description:
The backup operation that started at '2011-2-5:' 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 '0x80780021'. Please review the event details for a solution, and then rerun the backup operation once the issue is resolved
查找到已有MS博客描述類似問題，在遵循其方法後問題依然存在，已進行如下修改:
在註冊表:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\SPP
創建新DWORD值命名爲"CreateTimeout",值爲12000000.
發現博主可能忽略其他一些相關操作，在進行上述註冊表操作後要進行以下操作:
重啓 BITS, VSS 和Com+ event system 服務，注意BITS服務重啓會中斷系統更新等依賴服務.
參考MS博客:
Windows Server Backup failed to backup with error 0x81000101
https://blogs.technet.microsoft.com/asiasupp/2011/08/01/windows-server-backup-failed-to-backup-with-error-0x81000101/