Is it possible to have 2gb for a dynamic virtual disk to load stuff like firefox and etc, but still be able to reclaim this memory upon high memory demand (like vmware)?
this is, in effect, what the linux kernel already does for you. If you load an app it is retained in memory. However, if that memory is needed elsewhere, then so be it.
i think 4gb could be a bit excesive. with 2gb you could run a VMWare session easily. DEpending on what you are doing i guess....
also you have to change a parameter in the kernel to get more than 900mb of ram. if that's the case the you will probably have to get the source code for your kernel, presuming it is a modified SuSE one and not a stock kernel.....