Failover of CIFS - Issues with DFS
2018-03-26 11:16 AM
Perhaps those of you who use DFS can help.
I have a pretty typical setup with a cluster at my prod site and a cluster at my DR site, with snapmirror protecting my CIFS. My hardware is AFF8080s running CDOT 9.
I have a DNS A record for my production CIFS SVM: Let's call it
and a DNS A record for my DR SVM. Let's call it
I also have a CNAME record pointing to the production CIFS SVM:
I use this name in my DFS namespace, so a typical target looks like:
During a failover, I will "float" the CNAME record over to my DR CIFS SVM:
I also change the Service Principal Names for the CIFS service:
setspn.exe -D HOST/usfs1.companyname.net USCIFSProd1
setspn.exe -D HOST/usfs1 USCIFSProd1
setspn.exe -A HOST/usfs1.companyname.net USCIFSDR1
setspn.exe -A HOST/usfs1 USCIFSDR1
I then force a replication in AD. Once the DNS change propagates, clients should be able to access the CIFS shares at the DR site.
The CNAME record is updated and responds correctly to pings.
The workstation can access the share if I browse directly via
However, when I browse to the network locations via the drive letter assigned to the namespace, i.e.
or the UNC which uses the namespace, i.e.
I receive an error: The network path cannot be found.
A wireshark trace reveals a Kerberos mismatch. So it's not a network issue; it's that Kerberos is failing.
I have tried using KLIST to purge every ticket I can think of, including those of the network service, and the local system account. I have also purged the DFS caches using DfsUtil. All to no avail.
I do know that the client gets its DFS info through the Workstation Service. And, restarting the Workstation service (or rebooting the client) clears the issue.
So, question one:
1) Is there a way to remedy the issue without rebooting the clients (~1500) or restarting the Workstation service?
2) If not, is there another/better way to engineer the failover? I am NOT willing to move my CIFS service to a Windows environment as many have suggested, for many reasons.
I've considered instead modifying the links in the namespace directly via a script but this would obviously not be preferred as I'd much rather change one CNAME record than 2000 DFS target links.
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