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Windows 2008 DFS - Random slow browsing

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Windows 2008 DFS - Random slow browsing

Postby guest » Thu Jul 29, 2010 11:46 am

Hiya,

Got DFS setup between 2 file servers seperated by a 2Mbps WAN link. The Namespace service is installed on all 3 of our DC's (2 main office and 1 branch office). The Replication service is installed on both file servers (1 main office and 1 branch office).

Replication itself seems to be working fine.

However, every now and again browsing DFS shares will be slow, as in 30+ seconds to bring up the folder list. Once it loads, is resumes acceptable browsing speeds. Then randomly will revert to being slow.

This happens on both servers and clients.

Any ideas?

Thanks
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Re: Windows 2008 DFS - Random slow browsing

Postby guest » Thu Jul 29, 2010 11:46 am

Hi,



Yes, “sites” referred in my previous post is Active Directory sites.



Regarding this kind of network performance issue, it is necessary to enable network monitor, and even enable the trace to perform analysis/troubleshooting. However, please understand that it could be time consuming to analyze these trace logs. Also, forum is not the best resource to troubleshoot this kind of issue. I’d like to recommend that you contact Microsoft Customer Support Service for assistance. The support professionals there can provide one-one instant support for you so that the issue can be resolved more efficiently.


To obtain the phone numbers for specific technology request please take a look at the web site listed below:
http://support.microsoft.com/default.aspx?scid=fh;EN-US;PHONENUMBERS





Before that, here are some steps that you can perform on the DFS clients to analyze/troubleshoot this issue:



1. Access the DFS share by using IP address.

2. Access the DFS share by typing the specific file server computer name. For example: \\computername\share

3. Perform a clean boot:
http://support.microsoft.com/kb/331796



Additionally, please understand that, after the DFS clients start, they need to access the DC/root server to obtain referrals at the first time they access the DFS share. Then, DFS clients store the root referrals and link referrals in the referral cache (also called the PKT cache). The next time they access the same DFS share, they will check the cache and access the target folder directly instead of accessing the DC/root server again. However, there is an expiry time for each referral. If the referral has expired, the client will need to obtain a new referral the next time the client tries to access the DFS share.



Therefore, it could be normal that the DFS clients spend more time to access the share folder at the first time after they start.


For more information about the referral proces, refer to the following article:

How DFS Works
http://technet.microsoft.com/en-us/library/cc782417.aspx
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:09 am

In our case, we hadn't set the DfsDnsConfig registry key on our domain controllers to 1, as is required when using DFS in a DNS-only environment.

When we originally setup DFS in our enviroment we did read the various articles about how to configure DFS for a DNS-only environment (e.g. Microsoft KB244380 and others) and were aware of this registry key, but had misintepreted the instructions on when/how to use it.

KB244380 says:

The DFSDnsConfig registry key must be added to each server that will participate in the DFS namespace for all computers to understand fully qualified names.

We thought this meant that the registry key has to be set on the DFS namespace servers only, not realising that it was also required on the domain controllers. After we set DfsDnsConfig to 1 on our domain controllers (and restarted the "DFS Namespace" service), the problem vanished.

Obviously we're happy with this outcome, but I would add that I'm still not 100% convinced that this is our only problem - I wonder if adding DfsDnsConfig=1 to our DCs has only worked around the problem, rather than solving it. I can't figure out why the DCs would be trying to lookup DOMAIN (the domain name itself, rather than a server in the domain) during the DFS referral process, even in a non-DNS-only environment, and I also know I haven't set DfsDnsConfig=1 on domain controllers in other (admittedly much smaller / simpler) DNS-only environments and haven't had the same issue. Still, we've solved our problem so we are happy.
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:09 am

This could be caused by the DNS server netmask ordering. We came across this recently in Server 2003. This depends on your current subnetting.

Example.

Site 1: IP subnet 10.0.0.0/24 Site 2: IP subnet 10.0.1.0/24

Client in site 2 makes a DNS query for your domain based namespace and will be given the DFS server in site 1 by default as the DNS server is not aware of the site IP boundaries. You need to tell your DNS servers what subnet mask to use to identify which IP addresses to respond with.

See http://support.microsoft.com/kb/842197
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:11 am

The Active Directory Team Blog has a Three part article ALL about DFS Delays.

http://blogs.technet.com/b/askds/archiv ... t-1-3.aspx

It covers the basics on the Referral Process, and then shows how to use various tools including dfsUtil and dfsDiag to discover the actual cause of the delays.

It helped me find my problem. Which turned out to be no Read permissions on the the share directory for Domain Users.
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:13 am

http://technet.microsoft.com/en-us/libr ... 50(v=ws.10).aspx This page actually mentions both Domain Controllers and DFSN, if that helps.

DFS Domain Controller and Root Server Registry Entries

The following registry entries are located under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dfs


on root servers and domain controllers. All entries are REG_DWORD.
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:15 am

So I used this article in my search. I set everything up and still had issues. After spending several days looking into the problem and excluding everything 'Microsoft' I guessed it was Network related. Turns out our WAN Accelerator was the issue. I had our Networking guys turn off acceleration for our Domain Controllers and everything got better.
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Re: Windows 2008 DFS - Random slow browsing

Postby chicagotech » Sat Aug 12, 2017 10:16 am

First check that all of the links in your Namespace are available and good. That is what happened in my case, there was still a link in the namespace to a server that was down, so the long pause when opening DNS was because it was searching for that server and failing. Once I disabled that link in DFS the long pause went away.
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