Hi,

Regarding the /Z switch. Not only does it slow down the copy process, it can lead to unresponsive SQL Server. As it happens. There is a bug of some sort with this combination: robocopy with /Z switch inside SQL Agent Job on Windows Server 2003 x64 and SQL Server 2005 x64. When connection was lost between server and destination location, Windows started to aggressively trim SQL Server memory. Server started to page, and slowed down to the point of unusability. SQL Server was not configured with Lock Pages in Memory privilege.

You can test this out by disabling network card on your destination location.