What Is The Lifespan of a USB Flash Drive?
The lifespan of a USB flash drive relates to three factors. In general terms, a flash drive will last much longer than you think and here are some details to help you understand the answer.
The three factors related to the life span of a USB flash drive are:
- How the drive is made
- Wear leveling technology
- How the drive is treated
Flash drives are a commodity product and (generally) driven by lowest price. With that in mind there are plenty of shortcuts a manufacturer can use to save time and money. What is important to understand, is knowing the quality of product you are going to use.
How the drive is made
A flash drive is made up of five primary components: The PCB (printed circuit board) the flash memory, the USB controller, the components and the soldering which holds everything together.
Printed Circuit Board (PCB)
Most promotional memory products (flash drives given away at trade shows) will use a two layer printed circuit board. Two layer boards are bad for use with any USB device, including a flash drive. The USB specification requires four layers for a product to be made to specification. A four layer board will include the, much needed, grounding plane of the PCB to insure transmission without interference from the trace lines. A two layer board is at a much greater risk of not performing as it should. If you received a USB at a trade show, don’t consider that device for “long term” or “important” storage options.
This is an image of a four layer USB flash drive by Nexcopy with Micron memory with write speeds of 12MB/s
Flash memory used in the production of USB drives stems from a sea of unknown factors. Flash drives are the bottom of the barrel when it comes to NAND memory as part of the BOM (bill of material). All the good quality NAND memory is used for more expensive products like phones, set-top boxes, communications hardware, etc… and the manufacturer of USB flash drives, is typically, the last tier of manufacturing consumption. With that in mind, one trick the flash manufacturers use, is down-sizing the memory wafer (NAND chip). Let us provide an example: Toshiba is the world’s largest memory manufacturer, and after production of say a 64GB chip, they test it. If the quality of the silicon cells in the chip are below a certain percentage, the chip gets downgraded to a 32GB chip. They test it. If the memory is still failing QC, it gets downgraded again. The process continues. So if you are dealing with a 512MB USB stick, you are dealing with the worst part of NAND memory chip. Very unreliable. The quickest way to test the quality of flash memory is test the write speed. For USB 2.0 product, if you see a write speed of 9-10MB/second or better… its’ good quality. For USB 3.0 if you see a write speed of 18-20MB/second or better you are dealing with good quality. A slow write speed means the silicon of the chip is having a harder time making the phase change (positive or negative) to save data to the memory chip.
The USB controller is the chip on the flash drive with all the brains. The USB controller is the gate keeper between the host computer and the USB stick. The chip allows the host computer to read or write data to and from the flash memory on the flash drive. Because the USB controller is the brain of the flash drive, it’s important to have a controller that performs well and is reliable. One of the most important features of the USB controller is wear leveling. This is also one of the most important aspects for defining the lifespan of a USB flash drive. More about wear leveling in a bit. For now, the important point is understanding the compatibility of the USB controller to that of the flash memory. The NAND memory market is very fast pasted. New technology is always developing. For this reason, the firmware inside the USB controller is very important. The firmware “marries” the flash memory to the device and creates a usable flash drive. There are many flavors of firmware for a single controller and it all boils down to how often the USB manufacturer updates those firmware tools. It is very possible to load firmware that is not optimized for the NAND memory used in the production of the flash drive. It’s also very possible the firmware is set for a different objective, for example, the firmware was set to be optimized for capacity rather than read/write speeds. The amount of control the USB factory has with these firmware tools is mind-blowing. The firmware tools are used to configure the USB stick to exactly what they want. In summary, there is no real way to test the quality of the USB controller and it’s firmware other than having an intimate knowledge and relationship with the actual manufacturer of the USB flash drive. The point to explaining the function of a USB controller is to show what a large impact it has on the overall performance of the drive.
The device components are the resistors and capacitors found on the PCB of the flash drive. Typically these are not an issue other than the fact of a flash drive is driven on lowest price. This means the components a factory uses to make a USB stick could be using the least expensive components available in the market. Again, the components are typically not an issue because the production process is so well established the quality of components are nearly identical.
Soldering is the process and material used to hold everything together. The solder is used to hold the NAND memory to the PCB as well as the USB controller, resistors and capacitors. However; if the soldering needle isn’t maintained and cleaned regularly or the solder material isn’t the right gauge or quality, you can end up with some big problems. The manufacturing of the internal items is a key element to the lifespan of a USB flash drive. The best method to determine how your USB device is built, pop open the case by using a razor blade on the case seem and take a look. If you see hot glue on the inside, or sloppy soldering work, don’t trust that flash drive with long storage needs.
Wear Leveling Technology
Wear leveling (also known as wear levelling) is a technique for prolonging the lifespan of USB flash drives. Wear leveling is an algorithm on the flash drive controller to minimize the number of writes to a single block. Wear leveling arranges data so the erase and re-writes are distributed evenly across the flash memory during the life cycle of the device. By doing this leveling, no single erase block on the memory prematurely fails due to a high concentration of write cycles to a single location. The wear leveling algorithm is part of the USB controller firmware. The wear leveling is an algorithm designed for the brand of controller used to the brand of flash memory used. Because there are many combinations of controller brands and flash memory brands, two types of wear leveling techniques are used with flash drives. Dynamic wear leveling and static wear leveling. Dynamic wear leveling uses a map to link logical block addresses (where data goes according to logic) to the physical flash memory address that holds the actual bit of data. It gets interesting because the dynamic algo will update the map when new data is written and old data is removed. The problem with this method is the map updates on the data replaced; so in theory a portion never written, never gets used. Thus making the device last a shorter amount of time. Static wear leveling address this problem. Meaning, the theory is the same as dynamic wear leveling; make a map of where data goes, but it also shifts data to unused portions of memory during the USB lifespan of the drive to insure longevity.
Wear leveling is very interesting but can be difficult to understand, so a Wikipedia read might be in order.
The wear leveling explanation is really the bit of information every other article is missing when talking about “the lifespan of a USB flash drive.” Because of this algorithm the wear level on the NAND memory is as minimal as can be… mathematically… and thus your flash drive should really last 100,000 write cycles to all the memory blocks not a straight up 100,000 write cycles to the drive as a whole.
How The Drive is Treated
This last topic is obvious, but worth discussing. For example, if you place your family photos on a USB stick and put the flash drive into your safe, there is no problem the files will be there, working and accessible in 15-20 years. The silicon holding the data will not change if the USB is put into safe storage without compromise. However; if the USB is in your pocket, car, backpack and constantly being handled, there is a great chance the solder we spoke about earlier will affect some portion of the device. When components and parts start falling apart, it is sure the device will not work. With that in mind, be sure you allocate the right device for the right type of job. Any kind of flash drive is fine to move data from one PC to another PC where the files can still be found on the hard drive of the computer.
If you plan to use the flash drive as an archive device, then consider this:
Don’t use a promotional flash drive given to you – too many unknown variables. If you cannot determine exactly who made the drive, then don’t use it to archive data. If the flash drive is small, like 2GBs or less, probably not the most stable memory.
For those still looking for a one word answer about the lifespan of a USB flash drive; the answer is: it varies!