2.4 Solid state carriers

Solid-state memories are electronic circuit storage devices without any moving parts. These have been developed since the 1950s using various technologies. Of particular interest in the context of this publication are the so-called flash cards, developed since the 1990s. As removable data carriers they come in various formats (SD and several others) and as so-called USB-sticks. With an increase in storage capacity, accompanied by a dramatic drop in price, they have become popular as removable data carriers and, more recently, as replacement for HDDs in lightweight notebooks.

2.4.1 Recording principle and stability. Flash memories belong to the group of non-volatile solid-state memories, which retain their information without power supply. The memory cells consist of transistors, which can hold their information for many years. While reading capacity is generally described to be indefinite, programming/erase cycles are quoted to be between several thousand up to one million. Because of their relative sturdiness against mechanical shock and extended temperature ranges, they were originally employed in military applications.

As to their life expectancy, no realistic guesses are available. This is of minor interest as long as prices are significantly higher than HDDs. This makes them (still) unattractive for longterm storage. Although, in general, flash memories have proved their robustness for short term storage, specifically for location recording even under adverse conditions, it is imperative not to rely on a single carrier but to copy the contents at the earliest opportunity to another storage medium before arranging transfer to a secure digital storage system.