Follow-up to wearing / caching question
Martin Egholm Nielsen
martin at egholm-nielsen.dk
Mon Feb 7 16:36:45 EST 2005
>> I've been tasked with approximating the lifespan of the flash
>> (JFFS2) filesystem embedded in our products. Is there a best method
>> for calculating the space required for a fixed-size file over a
>> given lifespan? If we want our flash filesystem to be available for
>> an approximate lifespan of 20 years, given the wear-leveling
>> duty-cycle of JFFS2, and an average block endurance of 100k
>> write/erase cycles, would I need 150% of the file's size? 200%?
=== 8< 8< 8< ===
> Another way to look at it is an imaginary 1MiB flash. You can write
> it 100k times, for a total of 100GiB written to it. With 600M seconds
> in your expected 20 years, that gives you ~160 Bytes/s average write
> speed. Not very much.
Then what about the pagesize and corresponding writebuffer - this may
have an effect, as well, when talking that slow write rates, right?!
> Is that the calculation you were looking for?
I liked it alot - thanks! ;-)
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