Flash cards memory write cycles limitations?
February 14, 2005 7:50 PM   Subscribe

Flash cards have a limited number of write cycles per area of the memory (cells). While this may be very high, for the time being, assume I'm going to use them up at some point. [MI]

Am I better off leaving data on the card to force new data to be written to a different area proactively, or will the card take care of evenly spacing new data to a least-written part (possibly the same controller that handles not writing to the dead parts when they do eventually wear out).
posted by Caviar to Computers & Internet (4 answers total)
 
It probably depends on the card you use, and might be practically impossible to determine without looking at the controller firmware or talking to someone very geeky at the company that makes it.

Assume 100,000 writes... you could erase the entire card 80 times every day for somewhere close to four years before you kill the card...
posted by odinsdream at 8:02 PM on February 14, 2005


SanDisk's Wear Leveling whitepaper (PDF) explains the structure of common flash cards and how data are written on the card. It appears that, in general, data are not spaced evenly across the flash device.
posted by AlexReynolds at 8:04 PM on February 14, 2005


There's also the whole FAT issue to consider. Any change anywhere on the flash will also require a change in the file allocation table, which is written in one particular location. Although the wear leveling may help in this case, since the FAT is relatively small and the blocks are relatively large (at least in that Sandisk whitepaper.)
posted by smackfu at 8:11 PM on February 14, 2005


Here's some information about a filesystem that takes wear leveling into consideration.
posted by odinsdream at 8:53 PM on February 14, 2005


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