Need to know how to calculate and allocate the server side bandwidth between two exchange sites for DAG replication

Question

Hi All,
Please have a look in to the below mentioned environment.
primary site :SITE 1
server 1 
server 2 
secondary site :SITE 2
server 3
Note : All the above three servers are in single DAG .All the database are mounted on the server (server 1) which is located in the primary site (I.E SITE 1).
On that 5 databases we are having 3500 users .Based on the user designation we have allocated the mailbox size.
Query : Each and every day we are having the large no copy queue length for all the five databases to the server located in SITE 2.
Please help me out on this and also tell me is there any tool available to exactly get the required bandwidth for the exchange servers located between the active directory sites.
Thanks & Regards S.Nithyanandham

Answer 1

I don't know of any tool that can calculate things for you but latency is the biggest thing you have to worry about. The other issues is looking at the network gear between the 2 sites. I have seen many times were switches get maxed out if they are set to
1 GB or even ports getting maxed out and need to bonded for more throughput. Test your latency from the edge of each site then test it within to see if there is a difference. 
Regardless of their geographic location relative to other DAG members, each member of the DAG must have round trip network latency no greater than 500 milliseconds between each other member.
As the round trip latency between two Mailbox servers hosting copies of a database increases, the potential for replication not being up to date also increases. Regardless of the latency of the solution, customers should validate that the networks between
all DAG members is capable of satisfying the data protection and availability goals of the deployment. Configurations with higher latency values may require special tuning of DAG, replication, and network parameters, such as increasing the number of databases
or decreasing the number of mailboxes per database, to achieve the desired goals.
Round trip latency requirements may not be the most stringent network bandwidth and latency requirement for a multi-datacenter configuration. You must evaluate the total network load, which
includes client access, Active Directory, transport, continuous replication, and other application traffic, to determine the necessary network requirements for your environment.
http://technet.microsoft.com/en-us/library/dd638104(v=exchg.150).aspx
DJ Grijalva | MCITP: EMA 2007/2010 SPA 2010 | www.persistentcerebro.com