Why Did Microsoft Pick “16” As The Maximum Number Of Servers In A DAG?…
I was asked this question today. Why did Microsoft pick “16” as the maximum number of servers that you can have in a DAG? Having 16 servers in a DAG means that you can have a maximum of 16 copies of a database (one active and 15 passive). Isn’t it a bit too much to…
I was asked this question today. Why did Microsoft pick “16” as the maximum number of servers that you can have in a DAG? Having 16 servers in a DAG means that you can have a maximum of 16 copies of a database (one active and 15 passive). Isn’t it a bit too much to have 15 passive copies of a database? How can you justify this figure?
These were the questions that bugged an exchange admin that I met. To make it clear, the Exchange team didn’t go for a “magic” number for the maximum number of servers in a DAG. The limit is imposed on the DAG by the underlying Windows failover clustering, on which DAG is based.
The Windows failover cluster can only support a maximum of 16 nodes. This limitation kind of flows into DAG. So, though a DAG can only have a maximum of 16 servers, the limit actually comes from the Windows failover cluster.
There you go, the story behind the magic number
Thanks for sharing this information. How many database can be added in single DAG ? Is there any limitation ?
You can have a maximum of 100 databases (active and passive combined) on a server if you have an Enterprise license and 5 if you have Standard edition of Exchange.
In Windows Server 2012, maximum cluster node supported is 64, then why Exchange 2013 still support only 16 nodes ?
It is an Exchange limitation, not a Windows one. Why would you need to have a DAG with more than 16 nodes when the max database size is 2TB?
Thanks for clarification on it, prior i was thinking it designated for DAG only 16 copy while it imposed by windows clustering features :-)
Is it possible to have multiple DAG’s in single Exchange Organization?
Yes Muralee, you can have multiple DAGs