What is the difference between the two DFS Replication Group Types?

What is the difference between DFS replication group types - multipurpose replication group and replication group for data collection?

• Is it really only that replication group for data collection only allows 2 way connection, while the other one allows more than one?
• Is there any issue running only 2 servers (or disadvantages) in Multipurpose replication group?
• If there is no big advantage to replication group for data collection, should I always choose Multipurpose replication group so I can add more servers in the future if I so desire?

Thanks!

EDITED:

Additionally: From MS documentation (http://technet.microsoft.com/en-us/library/cc780303(v=ws.10).aspx): "This option sets up a two-way replication between two servers, such as a branch server and a hub server." Is the "Replication group for data collection" two way or one way? From what you describe it sounds one way, but from the documentation it says "two way"? And to clarify what I mean by one or two way:

• 1-way. Server A is replicated to Server B. Items on Server B do not go back to Server A.
• 2-way. Server A is replicated to Server B and items added to server B is replicated to server A.

•Is it really only that replication group for data collection only allows 2 way connection, while the other one allows more than one?

True. You can think of a Replication Group for Data Collection as a hub with a single spoke. The end points can be clusters as well as individual servers. You can create additional replication groups for data collection that point to the same hub, to make additional 'spokes,' but they will be treated as separate replication groups.

If you go through the wizard for creating a Replication Group for Data Collection, you'll see that it only gives you the option to set up 2 end points called 'Hub Server' and 'Branch Server.' Very specific use case.

•Is there any issue running only 2 servers (or disadvantages) in Multipurpose replication group?

No problem with that at all.

•If there is no big advantage to replication group for data collection, should I always choose Multipurpose replication group so I can add more servers in the future if I so desire?

You should choose Multipurpose if you want any sort of advanced replication topology. (Fully meshed, hub and spoke with many members, etc.)

From the Storage Team's blog at Microsoft:

... select the type of replication group to be created. The ‘Multipurpose replication group’ can be used to configure custom replication topologies. This type of replication group can be used to create replication topologies such as ‘hub and spoke’ and ‘full mesh’. It is also possible to create a custom replication topology by first adding a set of servers to the replication group and then configuring custom connections between them to achieve the desired custom replication topology.

The second type of replication group (‘Replication group for data collection’) is a special type of replication topology and is used to add two servers to a replication group in such a way that a hub (destination) server can be configured to collect data from another branch server. Let’s select ‘Multipurpose replication group’.

The 'Replication group for data collection' is really a special use case. If you want any other type of replication topology besides what is described in the second paragraph, then you want to use a Multipurpose replication group. You cannot just keep adding new members to a data collection replication group, though you can keep creating additional replication groups that all have the same hub server, to make up a kind of hub and spoke topology, if you had multiple 'branch offices.'