Justin está parcialmente correto, mas a cópia de sombra e o histórico de arquivos não são os mesmos. A cópia de sombra não existe no Windows 8, o Histórico de arquivos usa o diário de alterações do NTFS para controlar as alterações. Veja abaixo para detalhes.
De Wikipédia :
Both Backup and Restore and the "Previous Versions" interface, features that used Shadow Copy, have been deprecated on Windows 8 in favor of the new File History function. Unlike Shadow Copy, which performs block level tracking of files, File History only utilizes the USN Journal to track changes, and simply copies previous versions of files to the backup location.[42] Shadow Copy itself is still available for other software to use; additionally, it is still possible to access previous versions of shared files stored on a Windows Server computer.[80]
Extraído de aqui
There can be issues with Shadow Copies, so moving away from this seems like a good change. "One disturbing thing I did learn about Windows backup is that it uses NTFS Shadow Copies to keep prior versions. One (IMHO) extremely dangerous result of this is that if you ever connect your backup disk to a Windows XP system you'll loose all the prior versions, since XP's version of NTFS doesn't understand multiple shadow copies and so silently deletes everything except the most recent one. This raised all kinds of red flags for me since when I started with Windows 7 I was using the same backup drives to back up both it and my older XP system."
Então, basicamente, o backup do Windows 7 usou rastreamento de arquivos em nível de bloco e cópias de sombra, enquanto o Windows 8 usa o diário de mudanças NTFS para detectar alterações e copia arquivos para um local de backup escolhido pelo usuário, que pode ser um compartilhamento de rede.
Este é o blog oficial de MSDN .