De link :
In File Backup, Volume Shadow Copy Service is used to create consistent copies of files that are open or in use by applications. During the backup process, the backup app reads from these consistent copies. This is handy, for example, when backing up a .pst file that is constantly opened by Microsoft Outlook®. Volume Shadow Copy Service ensures the backed-up .pst file is in a consistent state so that it can be accessed upon restore.
Não tenho certeza se isso garante consistência em arquivos diferentes, mas presumo que o mesmo serviço seja usado para o Windows Server, onde seria fundamental garantir que o cenário fosse atendido ...