I've got two questions - how does Exchange 2010 do group expansion, and how do I determine the number of GCs I need for a given number of users/servers. Suppose I'm building datacenter with about 60 Exchange 2010 servers, each having the multiple CAS/MBX/HT roles, and supporting 120K users. First question is how do these servers choose which of the many local (same site) DC/GCs which to query to do distribution group expansion? I've found some info on Technet that tells me that Exchange 2010 has improved how it does group expansion, but there's not many more details other than settable memory limits. What algorithm is used to locate DC/GCs here? Is it like round robin through DNS, or just pick a random server from the site and see if it responds”? Then the next question which would follow would be: how to size the number of GCs required to support this number of users/Exchange servers? Regards, -fitz

I've got two questions - how does Exchange 2010 do group expansion, and how do I determine the number of GCs I need for a given number of users/servers. A) Unless otherwise specified on the DL itself, any Exchange HT can expand it. This is why you should make them universal. Also if Moderation is involved (which 2007 doesn't support) you should ensure a 2010 box is doing the processing. B) "For Exchange 2010, we recommend that you deploy one 32-bit global catalog server processor core for every four Exchange 2010 Mailbox server processor cores, or one 64-bit global catalog server processor core for every eight Exchange 2010 Mailbox server processor cores. Although other server roles will influence the number of global catalog processor cores required, the Mailbox servers that are deployed influences the deployment of each of the other roles, so basing the number of global catalog processor cores on Mailbox server processor cores will suffice" http://technet.microsoft.com/en-us/library/dd346701.aspx Mike Crowley: MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging Administrator Check out the new virtualization exams!

Suppose I'm building datacenter with about 60 Exchange 2010 servers, each having the multiple CAS/MBX/HT roles, and supporting 120K users. First question is how do these servers choose which of the many local (same site) DC/GCs which to query to do distribution group expansion? I've found some info on Technet that tells me that Exchange 2010 has improved how it does group expansion, but there's not many more details other than settable memory limits. What algorithm is used to locate DC/GCs here? Is it like round robin through DNS, or just pick a random server from the site and see if it responds”? Then the next question which would follow would be: how to size the number of GCs required to support this number of users/Exchange servers? A) Use this calculator to get started. You typically start with how much storage you are going to give users, then decide your HA/DR options. From there the calculator can help with the ratios. (60 servers seems WAY high for 120k users) B) "By default, whenever an Exchange 2010 server starts, it binds to a randomly selected domain controller and global catalog server in its own site. You can view the selected directory servers by viewing the properties of the Exchange 2010 server in the Exchange Management Console or by using the Get-ExchangeServer cmdlet in the Exchange Management Shell. You can also use the Set-ExchangeServer cmdlet to configure a static list of domain controllers to which an Exchange 2010 server should bind or a list of domain controllers that should be excluded. " http://technet.microsoft.com/en-us/library/aa998561.aspx C) the RAM reommendations for GC is to ensure its got enough to cache the whole ntds.dit database with room to spare. Mike Crowley: MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging Administrator Check out the new virtualization exams!

The command NLTEST will show the GC to use: NLTEST /DSGETDC:<domain> /GC “Exchange does a pretty good job of load balancing its requests across the domain controllers available to it, including taking into account how busy the DCs are with other work. So Exchange is not likely to be the site bully. But it is a demanding application and will present steady, relatively high load across all the GCs available in the site” ----------Refer to <Guidance on Active Directory design for Exchange Server 2007> Per my knowledge, exchange server will follow the following criteria to use the DC/GC: · DNS weight · Response speed · Round robin if the DNS weight isn’t the concernJames Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com