Office files are opening slowly from DFS folders

Question

Two weeks ago opening OFFICE files from DFS folders takes more than 15seconds. PDF/Image files are open quickly. If I change the extension of an office file to .txt I can open it quickly in any associated text editor.
I made some tests (DFSR health report, dcdiag, dfsutil ) and I did not find any problem.

After these I made more test to open the same file using UNC.
\domain\dfsroot\folder - office file opens slowly

\dfs1.domain_suffix\folder - office file opens slowly
\dfs2.domain_suffix\folder - office file opens slowly

\dfs1\folder - office file opens quickly.
\dfs2\folder - office file opens quickly.

I have found posts about the same isse without any usefull solution to it.
site1 (dc1, dfs1) <-> site2 (dc2, dfs2)
Windows 2012 R2 running on these servers.

Client OS (Windows 10/11), Office (365,2013,2016,2019,2021)

Any help would be appreciated.
Zoltan

Answer 1

Hello

Thank you for your question and reaching out. I can understand you are having issues related to Office files are opening slow in DFS.

• DNS. Make sure your DNS infrastructure is working as expected. Make sure the names referred in the namespace are quickly resolved. Use NSLOOKUP to look.
  • Domain Referrals. Make sure the DC referrals are happening as expected. Use DFSUTIL CACHE DOMAIN to look at this cache.
  • DFS Referrals. Make sure the DC referrals are happening as expected. Use DFSUTIL CACHE REFERRAL to look at this cache.

You might want to flush the caches before looking into those.

• For DNS, clear with IPCONFIG /FLUSHDNS
• For DC Referrals, clear with DFSUTIL CACHE DOMAIN FLUSH
• For DFS Referrals, clear with DFSUTIL CACHE REFERRAL FLUSH

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