Hard disk performance is the key
Use raid 10 it is the fastest
Use separate drives one for source files one for result files and one for sorting
Measure hdd/raid performance yourself using HDtach
Do not trust manufactures hdtach will tell you real numbers.
So you will be able to tell yourself in advance how long will it take to process 10gig file
It is all deepens on how mb/gig per second you raid can do
Happy sorting
Mike