I’ve inherited a situation in which two sister companies have increasingly grown closer together. At the start the two companies were completely separate from each other, however both companies now share the same Accounting, HR, Marketing, Sales, Customer Service, IT, Software Development, etc. Each company has its own domain in its own forest. The band-aid to get us through was creating a two-way trust between the domains and while that works for sharing resources it’s growing ever more time consuming to maintain and will only get worse the larger the companies get. All DC’s are fairly new hardware (2 years old) all running Win Server 2008 R2. All clients are Win7. There is no Exchange server.
Forest 1, Domain ABC = 390 users & computers, ~5 Servers
Forest 2, Domain XYZ = 270 users & computers, ~5 Servers
Here are my questions:
1. Would you recommend migrating the users/computers/servers from domain XYZ into domain ABC managing it as a single domain or create a second domain in Forest 1 and then migrating users/computers/servers from domain XYZ to this new domain?
2. What is the absolute safest way (least amount of risk and downtime) to migrate the users/computers/servers from domain XYZ to ABC? Have you used third-party software that’s made the transition easier or safer that you would recommend?
3. What phases or steps would you break this into to provide a fallback plan should the migration of the servers prove problematic? Is it possible and would you recommend slowly migrating say 20 users/computers per week and leaving the servers until the very end?