Re Enabling a disabled replication group member, without losing data as PreExisting

2017-01-30

Question

_{Monday, January 30, 2017 8:35 PM}

Hi All -

We have 2 servers in this scenario

Server1 - Primary. All folder targets point to a share on this server and all prod data is placed here.

Server2 - Data from Server1 is replicated here for DR.

We have three main replication groups setup for this. I discovered a large backlog to Server2 for all three groups, and in investigating, found that on the MEMBERSHIPS tab of the replication group, both servers are set to disabled.

Checking my head here - To not have all of our prod data on Server1 moved to the pre-existing folder and screw my day, Ill need to enable Server2 first, correct, then after some time, enable Server1?

Thanks!

All replies (4)

_{Wednesday, February 1, 2017 2:39 PM ✅Answered}

So the answer is -

After initial replication, the primary server bit is wiped from AD and all members in the group are now just a part of a basic mesh topology. This we know from the documentation.

The part that wasnt clear to me is that when disabling via the MEMBERSHIP tab and not the connection tab, the one you re-enable first, becomes the primary member, thus any data on it, will *not* get moved to the pre-existing folder. This also starts an initial sync.

My presumption is that disabling from the connection tab, when re enabled, just continues on and just starts processing the backlog from the time when it was disabled.

_{Tuesday, January 31, 2017 6:33 AM}

Hi RichardCirrus,

First please install the hotfix below for the large backlog.

For server 2008/2008R2.

https://support.microsoft.com/en-sg/help/2387778/you-find-a-very-large-increase-in-the-dfs-replication-backlogs

For server 2012R2.

https://support.microsoft.com/en-hk/help/3172614/july-2016-update-rollup-for-windows-8.1-and-windows-server-2012-r2

And follow the blog about 10 Common Causes of Slow Replication with DFSR to adjust your configuration.

https://blogs.technet.microsoft.com/askds/2007/10/05/top-10-common-causes-of-slow-replication-with-dfsr/

Please also monitor the health report and event viewer, if there's more warning/errors.

In addition, here are the threads discussed before, you could take a look.

https://social.technet.microsoft.com/Forums/office/en-US/c5d6f127-207a-41a0-b8a7-a8b2f8f1e6ec/what-is-causing-this-huge-dfs-backlog?forum=winserverfiles

https://social.technet.microsoft.com/Forums/office/en-US/e26893b6-956e-413f-ac41-493dd56335f6/dfs-will-not-replicate-huge-backlog?forum=winserverfiles

Best Regards,

Mary

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_{Tuesday, January 31, 2017 4:15 PM}

Hi Mary -

Mentioned in my original post - the backlog was because the membership of Server2 was set to disabled, along with Server1 in the replication group for these folders.

I want to know which one to re-enable first so the data on Server1 isnt effectively deleted by it being moved to PreExisting.

How can I tell? How can I see which one is considered the primary in the replication group and once I find that, which one to enable first to get it back going again (without deleting the data on Server1). Thanks!

Richard

_{Wednesday, February 1, 2017 5:28 AM}

Hi,

You can enable or disable replication with specific members of a replication group. However, it is important to understand the ramifications of doing so. After a disabled member is enabled, the member must complete an initial replication of the replicated folder. Initial replication will cause about 1 KB of data to be transferred for each file or folder in the replicated folder, and any updated or new files present on the member will be moved to the DfsrPrivate\PreExisting folder on the member, and it will be replaced with authoritative files from another member.

And if all members are disabled for a replicated folder, then the first member that is enabled will automatically be made the primary member

https://msdn.microsoft.com/en-us/library/cc725867%28v=ws.11%29.aspx?f=255&MSPPError=-2147217396

And in fact for primary member is used only during initial replication. After initial replication is complete, all other replication group members will have the same content as the primary member.

https://blogs.technet.microsoft.com/filecab/2005/12/06/the-primary-member-in-dfs-replication/