Are objects cached twice (not symlinked) in lasttime and http ?

That's the basic question, and also, if they are named with the exactly same 
key string, and if i can modify the way they are named (or stored), to 
preserve some 'internal' file information, like the original file name on the 
source server, in the cached file's name (or in a file header ?). 
I'm talking about binaries like images or audio files, not text content.

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