DFS Primary doesnt seem to be primary

Question

_{Wednesday, September 23, 2009 1:18 PM}

I've recently put to gether two servers for our AD DFS. Both Win 2k8 using Domain Namespace and Full Mesh Topology. Let's call the two servers DFS01 and DFS02. When configuring replication I set DFS01 as the primary server. Here's what's happening (or not)

On one occasion I browse to the namespace and I am pointed to DFS01. I add/delete or modify a file. The next time I browse to the namespace I am pointed to DFS02. If replication has already occured then I obviously don't have a problem but if it hasn't (or never does, which is sometimes the case) then any changes I made previously that were saved to DFS01 are not there.

This also causes problem if two users access the same file, each on a different server, at the same time. Someone's information is going to be lost. It seems that AD is arbitrarily pointing users to whichever DFS server is first to respond.

Questions:

1. How does AD go about pointing users to a DFS server when they browse to the namespace?
   2. Shouldn't the primary server always be the only one being accessed as long as it is online?
2. If not is there a way to configure DFS so that I have an active/passive environment where everything is written to the primary unless it is offline and then the secondary/passive server takes over as the primary/active DFS server?

All replies (1)

_{Saturday, September 26, 2009 2:44 PM ✅Answered}

HI JC69,

1. How does AD go about pointing users to a DFS server when they browse to the namespace?

A1. Generally speaking, the DFS root server will give the response with several referrals to DFS servers, the DFS clients will redomly select the DFS referral if there is no site-subnet information configured. If the AD site information was configure to bind with DFS servers, the DFS clients will redomly select a DFS server in its Site.

For detailed explaination, I suggest you read this guide

How DFS Works
http://technet.microsoft.com/en-us/library/cc782417(WS.10).aspx

2. Shouldn't the primary server always be the only one being accessed as long as it is online?
3. If not is there a way to configure DFS so that I have an active/passive environment where everything is written to the primary unless it is offline and then the secondary/passive server takes over as the primary/active DFS server?

Primary member only takes effects during initial replication of DFS.

DFSR has the concept of the primary member, which is the member that is specified during the creation of a replication group to be authoritative.
During initial replication, if a file exists on both sending and receiving members, the folder context on the primary member is considered to be authoritative and wins out. In other words, if we set the new-added DFS member as the primary member in the replication group, it will be considered to be the authoritative member and it wins out during the initial replication. This will cause it overwrite the current replicated folder content on the non-primary member. Besides, the conflict files and folders won't be moved to ConflictAndDeleted folder during the initial replication.

Please note: after initial replication is completed the primary member is no longer primary and DFSR returns to being a normal multi-master replication engine. It is only during initial replication that a primary member is needed so that DFSR knows which set of data is authoritative to start with.

Ideally we should not allow users to access files on any DFS member server until initial replication completes on all members. If users are able to make changes to the data, during initial replication this will increase the time and it takes for initial replication to complete. Also, if a user changes a file on a non-primary member when that member is still doing initial replication, the file will be overwritten.

Hope it helps.

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