arrays, mmu, addressing choices

[Charles Hixson via Digitalmars-d-learn]

I have a rather large array that I intend to build. but much of it will 
only occasionally be used.  Will the unused sections automatically be 
paged out?  If it matters my system is Debian Linux.

This array will be indexed by a ulong.  Is there any reasonable maximum 
size?  I've considered segmented addressing anyway, in case that's 
needed to allow paging, and it will definitely be needed when I get 
around to concurrent processing, with different sections resident in 
different threads.  But if appropriate I could do that from the start.

The questions above are really for a normal array, but I'd also be 
interested in how using an associative array would affect them.

I expect to eventually be using more memory than I have RAM in my 
system, so designing for paging is going to be important.  (Before then 
I'll be adding more RAM and a larger disk drive, but if I complete the 
full design even a large disk is going to be small.)