Article first published as Why Flash Media Will Burn You on Technorati.
USB Flash drives are absolutely amazing, capable of storing up to ONE TERABYTE of data in the palm of your hand is miraculous. Gone are the days of floppies, and CD/DVD disc media is all but gone as well.
In addition, the fact that Flash media is supported by all modern operating systems, from Linux, Mac, Windows, and mobile devices, means you can quickly transfer files and media between them at will. Add in the fact that they are so convenient to carry around with you, and they come in so many different shapes and sizes, colors, and novelty designs. They are absolutely amazing.
Unfortunately, Flash media is NOT the utopian solution that most think it is. Many consumers have been lulled into a false sense of security, mistakenly thinking, or assuming, that Flash drives are somehow infallible, and choose to put all their most important information in them, trusting them blindly. Unfortunately, like all forms of digital storage, the media can become corrupted, and you can, and will, lose valuable, if not priceless information.
From a security standpoint, Flash media is an absolute nightmare of epic proportions for many reasons, for example DATA LEAKS and VIRUS/MALWARE, and others too numerous to even detail in this one column. The high probability of physical loss or theft of a USB flash drive (A quick search shows this happening over and over and over) is reason alone to never use it as a long term storage option. Even if it isn’t stolen, your data can easily be tampered with, and your data can easily be copied without you ever knowing it.
I frequently get into heated debates with people about these issues, so I decided to write this in depth look at Flash technology.
Let’s take a look at what flash is, the different types, their inherent vulnerabilities, and the reason I don’t use, trust, or recommend Flash media to be used for anything but extremely short term use, transferring or copying files from one system to another, or to hold data that I will assume will be lost. I use flash drives all the time, and I encourage their use, but it is important to be realistic and understand what their capabilities, and most importantly, their LIMITATIONS are.
First, let’s take a look and understand what flash media actually is, without getting TOO technical.
Flash memory is digital computer memory that is erased and re-written by electrical signals. Flash memory was originally developed from EEPROM (electrically erasable programmable read-only memory). There are two main types of flash memory, which are named after the NAND and NOR logic gates. The internal characteristics of the individual flash memory cells exhibit characteristics similar to those of the corresponding gates.
SLC ~ (Single Layer Cell) – Only has the ability to hold can hold one bit per cell. This is the most expensive type of Flash media available, as it uses less power, enjoys faster write speeds, and is optimum for both industrial uses, and holding critical data.
MLC ~ (Multi Layer Cell) – Can hold two bits per cell, storing twice as much information. MLC is usually used most in consumer products because it is less expensive than SLC. Unfortunately, it has a lower endurance limit, and less program/erase cycles per cell.
TLC ~ (Triple Layer Cell) – Sounds great when you hear it holds three bits per cell, has the lowest cost of all Flash media, with the highest density. The trade off downside, it has slower read and write speeds, and significantly lower endurance. Usually only low end products contain TLC media, and certainly not recommended for the storage of critical data.
SLC Flash has 10x more endurance than MLC Flash, and 20x more than TLC. This is why SLC is industrial grade Flash, while MLC is consumer grade.
How flash media works, and how it becomes corrupted.
Just like a rechargeable battery loses the ability to recharge after so many hundred charge cycles, NAND Flash memory also loses the ability to retain data after thousands of write/erase cycles. The older your flash drive gets, the less reliable it becomes. This limitation is normally specified by Flash manufacturers and referred to as ENDURANCE.
NAND Flash also has a specification called RETENTION, which expresses how long the flash memory cells within will maintain their programmed state while not under power bias. This measurement metric is sensitive to environmental factors, for example, high temperatures can reduce the duration of retention, as well as the number of read cycles can degrade retention, particularly true on TLC Flash media drives.
Most drive manufacturers don’t tell you whether the Flash technology they use is SLC, MLC, or TLC. As we outlined above, particularly low cost TLC Flash can lose data very quickly, corrupting your data and files.
High temperatures, or humidity can cause shorting of circuit boards or corrosion of contacts,
Flash data is frequently lost by removing the flash media from the computer or device incorrectly, or while data is still being transferred, causing file system damage, and in rare instances, this can also cause cell damage.
It is extremely important to safely remove Flash memory from a device and never unplug a USB Flash drive while reading or writing information.
Furthermore, of all that isn’t enough…
Deleted files on FLASH drives are not deleted. They are in fact simply hidden. Why? Flash uses the FAT (File Allocation Table) format to make it easy to use on multiple operating systems and devices. As Wikipedia succinctly explains it, “The FAT file system is a legacy file system which is simple and robust. It offers good performance even in light-weight implementations, but cannot deliver the same performance, reliability and scaleability as some modern file systems. It is however supported for compatibility reasons by virtually all existing operating systems for personal computers, and thus is a well-suited format for data exchange between computers and devices of almost any type and age from the early 1980s up to the present.” Therefore, when you “delete” a file, it just removes it from the directory on the drive, but the data contained inside the file is still there, easily recoverable by prying unauthorized eyes.
USB Flash drives and Flash media certainly have their place, enjoy their convenience, and novelty factor, just use them wisely. Never put anything on a flash drive that you can’t afford to lose forever.
J. D. Redmond ~ “Dr. Tech” ~ http://www.DrTech.co