Loading large amount of binary data into RAM

My application needs to load from MegaBytes to tens and even hundreds GigaBytes of binary data (multiple files) into RAM. After some search, I decided to use std::vector<unsigned char> for this purpose, although I am not sure it's the best choice.

I would use one vector for each file. As application previously knows file size, it would call reserve() to allocate memory for it. Sometimes the application might need to fully read a file and in some others only part of it and vector's iterators are nice for that. It may need to unload a file from RAM and put other in place, std::vector::swap() and std::vector::shrink_to_fit() would be very useful. I don't want to have the hard work of dealing with low level memory allocation stuff (otherwise would go with C).

I've some questions:

• Application must load the more files from a list it can into RAM. How would it know if there is enough memory space to load one more file? Should it call reserve() and look for errors? How? Reference only says reserve() throws an exception when requested size is greater than std::vector::max_size.
• Is std::vector<unsigned char> applicable for getting such large amount of binary data into RAM? I'm worried about std::vector::max_size, since its reference says its value would depend on system or implementation limitations. I presume system limitation is free RAM, is it right? So, no problem. But what about implementations limitation? Are there anything regarding to implementations that could prevent me from doing what I want to? Case affirmative, please give me an alternative.
• And what if I want to use entire RAM space, except N GigaBytes? Is the best way really to use sysinfo() and deduce based on free RAM if it is possible to load each file?

Obs.: This section of the application must be get the more performance (low processing time/CPU usage and RAM consumption) possible. I would appreciate your help.