what is the best practices for the number of DC our enviroment

Well , you should refer the IPD - Active Directory Domain Services from Microsoft, to understand the number of DCs require. I have attached the files for you. Refer them to clarify your doubts.

As stated by @Amit, keep at least 2DCs in each site provided they should be powerful enough. I do keep 3 in each site, since I have a lots of  AD integrated applications running in the net work + all of them are GCs too.



Zac.
IPD---Active-Directory-Domain-Services-v
IPD---Active-Directory-Domain-Services-v

thanks for advice

we have 2 new physical servers act as DC i will connect to one of them and change the operation master . i will change the  RID - PDC - infrastructure to one of them and this server will the primary one .  then i can remove the rest normal using dcprmo right ?

then i will get no effect ?

That is fine if you keep Domain Name master and Schema master on one server and rest FSMO role son another server.

you can remove using DCpromo without any issue, just keep checking replication time to time and I would suggest demote one DC only within 24-48 hours to see if there is any impact.

thanks again

for example i want to  dc1 and dc2  as physical DC servers

i want dc1 to have all roles  plus DNS master and DHCP master

so i found out how to move

from dc3 to dc1 these roles  

1- RID Master FSMO Role
2- PDC Emulator FSMO Role
3- Infrastructure FSMO Role

but i dont know how to move these roles to DC1

1- Schema Master FSMO Role
2- Domain Naming Master FSMO Role

because as i said i want DC1 to be everything plus DNS master and DHCP master

so please tell how step by step or provide some links for me  


thanks
sword

once i tried to move Schema Master FSMO Role i got this message

please check the attached file
7-27-2015-2-34-09-PM.png

Hope you are running the procedures on the DC, which you want to hold the FSMO Roles.

Have carefully read the article? Have you run regsvr32 schmmgmt.dll in the desired DC? It seems that you are not selecting the correct DC to transfer.

Zac.