What is Flash Memory?

Flash Memory is a form of non-volatile memory that can be electrically erased and reprogrammed. Non-volatile means that it does not need power to maintain the information stored in the chip.
Flash Memory has become the dominant technology wherever a significant amount of non-volatile, solid-state storage is needed. Examples of applications include digital audio players, digital cameras and mobile phones. Flash memory is also used in USB flash drives, which are used for general storage and transfer of data between computers.

Flash Memory vs. HDD
One of the limitations of flash memory is that although it can be read or programmed a byte or a word at a time in a random access fashion, it must be erased a "block" at a time. Once a byte has been programmed, it cannot be changed again until the entire block is erased. In other words, flash memory (specifically NOR flash) offers random-access read and programming operations, but cannot offer random-access rewrite or erase operations. When compared to a hard disk drive, a further limitation is the fact that flash memory has a finite number of erase-write cycles (most commercially available flash products are guaranteed to withstand 1 million programming cycles) so that care has to be taken when moving hard-drive based applications, such as operating systems, to flash-memory based devices .

In addition, flash memory offers fast read access times and better shock resistance than hard disks. Another advantage of flash memory is that it is nearly indestructible by physical means, able to withstand intense pressure and boiling water.
There are lots of angles that people consider when choosing flash versus HDDs. Price per megabyte is often discussed, but this must be weighed against total system cost, which is an equally important factor. In many applications physical size and weight, limit the use of HDDs. Energy consumption and robustness are arguments often discussed. One very important factor is file size, which is one of the top reasons for selecting one or the other media type.

Revenge of HDDs
Hard Drives are about to introduce perpendicular recording, this will result in larger densities up to 10 times what we currently have with just a few technological changes in the head designs and platter coatings used. Current hard disk technology with longitudinal recording has an estimated limit of 100 to 200 gigabit per square inch due to the Superparamagnetic effect, though this estimate is constantly changing. Perpendicular recording is predicted to allow information densities of up to around 1 Tbit/sq. inch (1000 Gbit/sq. inch).

Conclusions
The cost per byte of flash memory remains significantly higher than the corresponding cost of a hard disk drive, the small capacities comparing with HDDs, finite number of erase-write cycles is preventing Flash Memory for the moment from becoming a solid state replacement for the hard disk drive.

written by Cristian L.