The VM-NFS cache I'm referring to is NOT related to array cache and that's what I've been telling since beginning. It is nothing to do with 'write directly to HDD'.  This is a NFS related feature (available in all Linux/Unix platforms) leveraged here. By default any NFS file system is created with cache enabled option. This provides faster access for its clients either through exports or locally. In early versions of VNXe OE, it was observed that VMware ESX hosts perform very poorly with this NFS cache enabled. After lot of testing it was decided to provide an option to enable or disable this NFS cache (only for VMware ESX hosts). This caching is maintained separately at filesystem level and applies to only this particular file system. However, when cache is disabled for this filesystem, VNXe OE will still use its read cache or write cache for performing disk activity.   What I'm trying to say here is that you CANNOT disable VNXe disk read cache or write cache from the user level. VNXe OE will manage it dynamically. Normally write cache is automatically disabled when BBU is found faulted.
how do you disable cache on VNXe?  MR:4
VNXe Cache Disable