Subj : Re: Life Expectancy of Flash Memory Drives To : comp.os.linux,comp.os.linux.setup,comp.os.linux.admin From : Daniel Ganek Date : Fri Jul 02 2004 12:32 pm Stephen Moll wrote: > "Kenneth Lantrip" wrote in message > news:0nAEc.15407$J82.10525@fe25.usenetserver.com... > >>Yesterday, my PNY Atache flash memory stick drive started to fail on me. >>It can read all files just fine. So I managed to tar all the files into >>a backup. >> >>I can reformat it in Win2000 or Knoppix just fine. But when putting >>files (of any kind) onto it will lock up the computer (W2k or Knoppix) >>every time after about a minute or so of writing to the device. It does >>this on two different computers that I've tried. >> >>Conclusion: The drive is bad. >> >>My query is: Does anyone know about how long one should expect one of >>these type drives to last under daily use as a Knoppix persistant home >>directory? Anyone know of any utilities to lock out a bad memory >>cell/sector? >> >>I thought since these things don't have moving parts (other than moving >>from place to place) they should last quite a while and be very reliable >>from data loss. Guess I was wrong. >> >>Anyone else run into problems with flash memory? >> >>Thanks. >> >>Kenneth Lantrip >> > > > This type of device is almost undoubtedly going to be NAND based flash > memory. This type of memory is broken into blocks of 8 to 32k, each of which > has to be erased before it can have data written to it. Each block has a > life expectancy of 100,000 to 1,000,000 erase cycles. On top of that there > is a general MTBF (Mean time before failure) of around 500,000 hours. > > What this means is that after 100,000 erase cycles for a particular block, > there will be an ever increasing likelihood that block will start creating > errors. By 1,000,000 it will almost certainly have stopped working. Even if > none of the blocks in your memory device have had less than 100,000 erase > cycles, the device as a hole is expected to fail at some point, with the > highest probable failure time in 500,000 hours (over 50 years). > > Remember that these figures are based on probabilities, and a manufacturer > can only really say that ninety-something percent of devices will meet these > figures. There will be a small percentage that fall outside either by > failing earlier than expected, or if you're lucky... later. > > All of these devices have defects in them when made, and part of the > manufacturing process involves something akin to formatting where bad blocks > are marked as bad on the chip. Some may pass the test at manufacture only to > fail soon after. For mulitmedia storage this isn't usually a problem as > small numbers of bit glitches are lost in the noise, but for program storage > this can be a problem... obviously. > > So it really depends on what you use it for. I have known people use them as > system storage on PDAs, running alernative operating systems from them, only > to be surprised when the system becomes unstable after a few weeks. I have a > USB stick, which I've had for about a year. I actually store software on it, > but the contents are rarely changed, only once or twice a month, and it is > still fine. > > Do you use it heavily? > > What about mechanical shock? They are easy to drop, etc. /dan .