Browsing posts in: random observations

Flash memory reliability

During my trip to China a few weeks ago I met Ernst Fuld again. Ernst is CEO of the NGN, the dutch IT-professional platform. He told me that he has tried to test some usb-sticks and see if they could be written and erased so many times that they break. As you probably know, flash memory can only be written a limited number of times. Each time you erase (rewrite) the memory cell, there is a slight chance that it breaks. Normally, the memory is guaranteed to last for 100000 rewrites, but has anybody tested this on a regular usb stick?

There is a problem however. The sticks are known to use a technique called “wear levelling”. The data you write to the stick is remapped to memory area’s where the number of rewrites is the lowest. This means that you cannot test 1 cell by re-writing a small file over and over. You have to fill the WHOLE stick in order to rewrite all cells. And even if you manage to break a cell, there is also error-correction logic and bad-block remapping that will correct the error without notice. So the flash memories seem to be unbreakable.. or not!?

That’s why I wrote this simple app: Flashkiller. It’s a free download so you can test the reliability of your memory stick yourself. If you broke a usb-stick or memory card with it, please respond to this post!

May 2 update: the kingston 512mb is now @19000 rewrites and still without an error..

june 13 update: The kingston is DEAD. After 65000 writes it becomes a read-only stick. Nothing can be written any more, and when i try to write it gives an error!!!!