The maximum cache size is 256kbytes. I don't know the size of the file, it seems not very large to me.
The given stream is a test stream and contains a repeated video, i think the video may be around 10MB.This evening wil be a live stream that wil run for an hour. I hope this stream will be cached before it starts.
I tried to add cache exceptions for this stream, but that also doesn't seem to help.