BIG-IP : iControl : LocalLBDataGroupFile.set_local_path() : swap large file under load

I suggest you raise a support call with F5 if you experience any "site down" type failures. I have seen TMM crashing, core-ing and re-starting under heavyload with some iControl calls before and the impact varies version-to-version.

You need to examine the LTM logs at the time the VIP came down - there should be plenty of log messages informing about the reason for the service interruption.