You may still be able to mitigate this by lowering the max open files in your Mango/overrides/properties/env.properties file. In specific, the
#Set the number of files the database can have open at one time
property. The comment is somewhat misleading, what this number really means is the maximum number of output streams that can be held open. Setting this to 0 would tell the database to always close files after every write, which would encourage flushing to disk (I believe MAPPED_BYTE_BUFFER streams may not be flushed until a subsequent garbage collection)
The downside would be that buffering is done for a reason, which is efficiency, especially when points are receiving fairly rapid writes. So, performance can be affected.