> The more modern flash drives, made within the last 2 years or so, are much
> more durable than the older ones

I think he is referring to the amount of write to the usb type memory. Puppy has the whole file system in RAM and only writes back to the usb drive every 30 minutes or so. The is supposed to increase the life of the usb drive.

visionary

the newest flash drives (at least the good ones), have "controlers" the assure, that the writing on the memory is homogeneous, that is that one place in the chip is not writen many times and other one is writer less, this assure a life time much longer then the older ones. i have a corsair voyger gt that acording to corsair have a 100.000 write cycle life. that mean i can write 210gb of data per day for 10 years. i guess this is enought cause i will probably lost the pen drive before that.

link to the doc http://www.corsair.com/_faq/FAQ_flash_drive_wear_leveling.pdf

sadrunk

Flash memory, whether it be USB thumb drive or media card, comes in two flavors: SLC or MLC. SLC stands for Single Level Cell — traditional binary memory where each cell is either zero or one. MLC stands for Multi Level Cell — each cell can represent two or more bits. MLC memory is less expensive because it take less real estate for a given size. Most consumer flash memory is MLC for competitive reasons. The disadvantages of MLC are:

Most manufacturers of flash media are loath to tell you which they use, or specify endurance, for fear of exposing their inferiority. SanDisk, for example, makes no mention of SLC or MLC, and omits any mention of endurance, even in their OEM flash memory documentation. They apparently subscribe to the marketing theory that if you keep the customer ignorant, he/she will be dumb enough to buy your product. Transcend (www.trandsendusa.com) is more forthcoming about the technical aspects of their products.

As sadrunk mentioned above, flash media have a controller that implements wear leveling, spreading the erase/write cycles around to improve lifetime. As a practical matter in many applications, such as digital cameras, the SLC vs MLC question may be irrelevant. For critical applications, or where extensive writes are anticipated, SLC would be the better choice. This explains why Live CD type distributions are more suitable for flash based systems, why Tomas M's posting above is important, and why industrial compact flash cards and solid state disks utilize SLC.

Mike (mikep)

Thanks Mike for your insightful info. One further question,

Is there any way to tell if a USB thumb drive/media card a SLC or MLC based?

> that mean i can write 210gb of data per day for 10 years

sadrunk's flash must be SLC. Mine are the smallest and cheapest ones available on the market. I bet they are MLC. According to the endurance rate difference between SLC and MLC posted by Mike, at such writing rate, mine would wear out with a year or even a month.

No wonder there are people who don't care about the wear out of their flash media, and those who care a lot.

xpt

I don't know of any way to distinguish MLC from SLC in a flash drive if the manufacturer does not specify the type or the erase/write cycles. However, I wouldn't despair about the life of your flash drive if it is MLC. sadrunk posted the link to a Corsair document that explains wear leveling and estimates write capacity to be 120GB/day for ten years with an 8GB SLC flash drive rated for 100,000 erase/write cycles. If you have a 1 GB MLC flash rated for 10,0000 cycles, that still means you could expect to write 1.5GB/day, (divide 120 by 80) and that is a lot of data. You may be more dependent on error correction but the chance of a fatal error is very small. I use MLC compact flash cards as well as SLC because they are cheap and I know I will replace them before they wear out. This is one of those cases where you don't need a Ferrari if the speed limit is 100 km/hr.

Mike (mikep)

documented on: 2008-03-02