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DFS-R takes hours to replicate large file changes

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DFS-R takes hours to replicate large file changes

Postby guest » Thu Jul 29, 2010 11:20 am

I have been evaluating DFS-R in both Server 2008 RC2 and now Select code for use as a replacement to our current robocopy process. We move a number of virtual host disk files as well as fairly large 10-20GB database files.



I have set up a DFS-R replication group between two 2008 servers using full-mesh topology. The initial replication seems to work fine, and I can make small changes like file renames without issue. File deletions also appear to replicate in a timely fashion.



The problem I'm having is if I change a large file - either by copying it out of the replication source group and back in, or just a new big file (big as defined as 400MB - also have tried larger - same problem), it takes hours for the replication to happen. There is no network or disk activity on either server. It is also not a bandwidth issue - these servers are local with gigabit connections. I am trying to use remote differential compression as the final deployment will be over a slower 100Mb link.



I have run the reporting tool, and it shows that everything is fine. I occasionally get an error in the DFS event log event ID 5002 which says that "the DFS Replication service encountered an error communicating with partner <partner server> for replication group RepTest.



Additional information: Error 1753 there are no more endpoints available from the endpoint mapper.



I have plenty of disk space, and I have increased the staging quota to 24GB, which is much larger than the entire test folder.





Any ideas? I have high hopes for this in our environment, but I'm frustrated by the lack of a real-time management tool of some kind that can show the replication queue length, etc.



Thanks in advance,

TJ Cornish
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Re: DFS-R takes hours to replicate large file changes

Postby guest » Thu Jul 29, 2010 11:21 am

Hello,



We need more information in order to help figure out what is going wrong here. Could you please increase the DFSR debug log verbosity using the following command:

wmic /namespace:\\root\microsoftdfs path dfsrmachineconfig set debuglogseverity=5



The DFSR debug logs can be found in the directory 'C:\Windows\Debug'. Some of the older log files will be zipped with a .gz extension. After increasing the log verbosity, could you please try reproducing the problem?



We would need access to the debug logs after the problem has been reproduced. Please do also keep a look out in the event log for any events (Error/Warning) that DFSR generates.



Please also do let us know if you have any filter drivers (antivirus applications, backup applications, security/quota screener applications etc.) installed on your server.



Thanks,

Mahesh
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Re: DFS-R takes hours to replicate large file changes

Postby guest » Thu Jul 29, 2010 11:21 am

Thanks for your response. I ended up opening a case with Microsoft support. We have found that this situation is happening because of Microsoft Forefront antivirus. It is unclear as to what the exact cause is, but we have found the following observations:



When replication does not occur right away, it is because the source server doesn't see that there is a new file to replicate. The USN journal is not updated correctly.
Renames and deletions work fine.
We initially thought it was related to the size of the file. We have determined that it is not size related, but rather file type related. I had been testing with ghost image files of various sizes. By expanding the size range and types of files we were working with, we found that a 12MB Ghost image fragment does not replicate correctly, but a 350MB executable archive works fine.
Running the FSUtil USN command on the file that is not replicating causes the USN to be updated, which in turn causes replication of that file to resume.
Rebooting the source server also causes the stuck file to replicate.
The nightly Forefront AV scan causes the file to replicate.
My case is now in the hands of the Forefront team. They have a number of debugs and are trying to replicate the problem. The DFS group that I spoke with believes this is not a DFS issue, but rather a Forefront and USN journal issue.



I will post the final outcome to this thread when I hear back from the Forefront group.



Thanks again,

TJ
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Re: DFS-R takes hours to replicate large file changes

Postby guest » Thu Jul 29, 2010 11:23 am

The MS support team has given me a little more information:



The Forefront team has succeeded in replicating the problem. It appears that this issue is related to Forefront's interaction with x64 editions of Windows - in addition to re-creating the problem in Server 2008 x64, they also found it in Server 2003 x64 edition.
The problem also affects FRS.
The Forefront team has advised against installing Forefront on any x64-based domain controller because of the FRS issue - this could interfere with AD replication.
It appears that any file type that Forefront would typically scan, such as .EXE, .ZIP, .DOC, .TXT, etc. replicate fine. Unknown or non-executable file types such as .GHO .GHS, .XML, .INI all appear to have the problem. It is unknown if this is a hard rule, or if there is more involved.
I will continue to post any new information I get.
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Re: DFS-R takes hours to replicate large file changes

Postby guest » Thu Jul 29, 2010 11:23 am

Could you post the syntax of the FSUTIL USN command you used to get the replication of the problem file to work. You mentioned "Running the FSUtil USN command on the file that is not replicating causes the USN to be updated, which in turn causes replication of that file to resume." and we have a similar situation, though we are not using Forefront. We can't get a 20MB file to replicate over the WAN. Small files work fine. Thanks
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