I hope that here is the right place to ask for help.
We use a Stretch MetroCluster built with FAS3210 release 8.1.1 7-Mode.
On this infrastructure we use two volumes one is NFS for virtual machines which works fine and the other is CIFS for many shares used in the Windows environment.
In the Windows environment (win2k8R2) we have different clients (WinXP, Win7): PCs, laptops, and Wyse terminals for Citrix environment.
I am fighting with the "cifs.oplock.break.timeout" error from one year ago, with technical support from NetApp, Citrix, Microsoft, suppliers, we applied a lot of patches for Windows environment and upgrades for NetApp storage, but we had no luck.
The most important for us is that we cannot use Excel files (MS Office2010) with the share workbook options enabled.
Daily few excel files are blocked/freeze and because of this we loss data, the users session is blocked and so on.