The introduction of Windows 2008 (download link) brought us the famous Read-Only domain controller, the domain controller without passwords (unless explicitly approved) and one-way replication. That one-way replication also applied to the SYSVOL share. Sysvol is replicated by either FRS or DFSR depending on the initial setup of the domain. If you have upgraded your domain from Windows 2000 or Windows 2003 to Windows 2008 SYSVOL is still using FRS to replicate. When you have initially deployed Windows 2008 and set the forest functional level to use the Windows 2008 standards; DFSR is used. Usually the replication of Sysvol is two-way, you can change the contents on each domain controller and those changes are replicated to all domain controllers.