I remember having been advised that it was helpful to configure both Size and MemSize when setting up the Tridion broker cache. The idea was that if you only configured one, then the other would have its default setting, and that the smaller of the two would "win".
Today I discussed this with someone who had been advised only to configure one of these values, so I went to check the documentation (2011) and it says the following:
To configure the overall cache, use either Size or MemSize
It may be that this was an issue in older versions of Tridion, and that in current versions it only heeds one limit if you only configure one.
Do I need to configure both settings, or should I use only one?