Recommendation is 10,000 max per data mover but I have seen over 30,000

Of course it depends on your model and how much memory it has

I don’t think it has very much impact on the VNX performance itself – of course large numbers of shares have an impact on client when browsing the shares – as with any CIFS system

You can refer the document below for the CIFS guidelines for the latest Celerra version.(page no. 56)

https://support.emc.com/docu43521_Celerra-Network-Server-Release-Notes-6.0.65.2.pdf?language=en_US

Jithin