What is Flash Storage?

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What is Flash Memory?

Normal RAM memory (Random Access Memory) that is often used in computers is volatile. This means that when you turn off the computer, all the information that is stored in the memory chips is lost. In contrast to this, flash memory is non-volatile which means that the information stored on this type of memory technology is retained when the power is cut. Information written to and erased from these special memory chips is done electronically rather than in a mechanical way -- similar to the older and much slower EEPROM (Electrically Erasable Programmable Read-Only Memory) technology.

This form of solid state technology differs from mechanical storage like standard hard drives; the information in this case is stored using magnetism. The most common type of flash memory in use today is NAND -- this name is taken from the electronic logical gate NAND operator because flash memory uses floating gate MOSFET transistors that are arranged in a similar way.

How Does it Work?

As previously explained, flash memory uses floating gate transistors. These are arranged in a grid. Rather than a typical transistor that has one gate, flash NAND memory has two gates. Having two gates makes it possible to 'store' a voltage between the two gates so that it doesn't drain away -- this is very important and makes any information stored non-volatile. In fact, this 'trapped' voltage (which represents information) on the chip can stay in a locked state for many years -- or until you erase the memory.

Information stored is erased by draining the voltage away from between the two gates by using the special floating gate feature that is unique to flash memory technology.

Common Flash-based Electronic Devices

There are many consumer electronic devices that use NAND flash memory as storage. Some external storage solutions also utilize NAND flash memory.

The types of hardware that you are likely to come across that uses this type of technology include:

Advantages and Disadvantages

Like all technology, there are pros and cons of using it. One of the clearest advantages of using flash-based memory (and devices that utilize it) is that there are no mechanical parts that can wear out or easily suffer damage. For MP3 players and other devices that can play digital music, this is the perfect storage medium which is immune from vibrational shock, accidental magnetic erasure, etc. Flash memory is also relatively cheap and can be a good choice for storage -- for both manufacturers of hardware devices and consumers who wish to purchase extra storage in the form of memory cards too.

However, flash memory does have its faults. For starters, it has a finite life span in the number of times that data can be written to the same area of memory. This is known as P/E cycles (program-ease cycles) and typically has a maximum of about 100,000 read/writes. After this, the flash storage will decrease in reliability as the NAND memory deteriorates.

This memory wear can be evened out on MP3 players and other portable devices using firmware that spreads these read/write cycles out more evenly making the device last many years under normal usage. Another downside to flash memory is it still doesn't measure up to the TB (Terabyte) capacities that we see in mechanical hard drives and so this technology can't be used (yet) for mass storage on a large scale.