I haven't come across any limitation per se protocol, ultimately it all boils down to how the data points (LIFs) are doing and their load and client's kernel capability . What ontap version are you running on FAS3250?
To start with, follow standard troubleshooting steps: ( I am assuming cdot) 1) Begin with finding an overloaded LIF by comparing the number of connections on each LIF. Look for the 'count' on each Node. May be work re-distributing LIFs between Nodes. ::> network connections active show-lifs ::> network connections active show-clients -node <node>
2) What NFS versions being served?
3) Also, if you OCUM/AIUM, just have a look around how the Nodes are doing in terms of processing on different components such as node/aggregate/volume/data-processing etc.
This will give you some basic idea around the connections/latency overall and then you may be able to narrow down the cause. There are lots of tracing available in cdot that could help but I wouldn't go that far. If nothing helps, just raise a ticket with NetApp.
Just for reference, this may not apply to your case: