It seems that USB sticks and SD cards also follow Moore's Law, in that the storage capacity they offer doubles each year. A 64GB stick now costs US$ 40, and an 8GB stick, which used to be the market leader just a few years ago, has lost almost all its value and ends up in a drawer. At the other end of the product spectrum, prices rise disproportionately: Whereas a 128GB stick costs about US$ 80, one with twice the capacity, 256GB, is about four times the price.

Combining multiple storage media would achieve acceptable storage capacity at a low price, and, if you are looking for a software solution that combines multiple storage modules to create an array, something like Linux Volume Manager (LVM) springs to mind. It elegantly welds together your hardware to create software partitions, which  – at application level – feel exactly like hardware solutions cast in metal and plastic (Figure 1).

Knapsack Problem

Surely no one wants to jab the USB ports on their computer with a handful of USB sticks just to mount an LVM partition that provides access to a backup. It would be better to distribute individual files across the sticks. Scientific literature describes the method as a knapsack problem [1]. In this optimization problem in combinatorics, the task is to pack heavy items into different knapsacks, none of which may exceed its specific maximum weight.

[...]