we have around 800 users and 4 VMs act as exchange servers 2010 sp3
so we have 4 physical servers run as active directory domain controller 2008 R2 plus DNS and the same number as VMs that mean we have 8 DCs
i want to reduce the number of DCs but my colleague said NO it is important to have many DCs to serve the users and exchange activity .
is this true and why and what the best practices in such case
please if you can provide an article or doc talk about such case
thanks in advance