VNX Cifs with windows front end

We looked at one solution but it was mostly to accommodate Mac users. We had all kind of issues with permissions (just like you alluded earlier) plus having that single point of failure (your windows server) did not work for us.

Secondly if anyone using CIFS in a large windows environment what the most success they have had for AV protection.
We have had a terrible outbreak of the Porn trojan that takes all the folders hides them and creates executables with the folder names. We have slowed it down by using file filter with .exe extension to keep non admin users from creating executables but its not a fix. I have tried symantec and mcafee with CAVA and it does not detect this one as its not a "virus".

Have you ever had issues with the AV service on the NS80 stopping mid full scan?

Yes, in fact, which is why we spin up a completely different set of VMs to do full filesystem scans.  If your NAS is very busy, you can run short on CIFS threads for CAVA scans.  So short, in fact, that the real-time scans will continue work (albeit slowly) but your full scans get killed off for lack of threads.  You can increase the number of reserve threads for CIFS (its in the CAVA docs), but you have to restart CIFS as a result.

We had roughly 8000 users against our NS80 on DART 6.x.  We were using McAfee 8.7i on four physical and 4 VM (Microsoft Hyper-V) CAVA servers, all running Windows 2008 R2.  We had pretty good daily protection without many issues.  However, at times McAfee would lag tremendous on "Zero Day" outbreaks, but we had decent GPOs in userland, limiting the effectiveness of malware on the desktops.

Most AV providers will have point in time where they're just not as fast as "Vendor X" for finding something.  Our approach was to continue to use McAfee for daily protection, but we spun up extra VMs to run a scheduled AV scan of user home directories as a precaution.  This took about 6-8 days for an 8TB filesystem.  If the AV clients on your desktops are up-to-date, this might work for you.

That isnt really feasible – you cannot just mount CIFS shares from one server and re-export them

Besides you still wouldn’t get NTFS that way

Of course you could use the VNX storage a FC/ISCSI block storage and use it on a Windows servers

Then you need to live with the Windows downfalls