cf wear levelling strategy

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Hi,

    This link has docs about the wear levelling strategy of sandisk
industrial compact flash. Since it has been discussed here several times
I decided to post it.

http://www.sandisk.com/industrial_cf_memorycard.html

Re: cf wear levelling strategy
Quoted text here. Click to load it

Apparently, this is for the newest CF only, have not tried any yet.

"SanDisk is the only company that offers a complete line of Industrial
Grade (IG) Flash memory cards"

Industrial grade - 2,000,000 cycles
New standard grade - 300,000 cycles
Old standard grade - 100,000 cycles

For most existing CF: old standard grade with 1000 clusters (est.).

Writing 1 byte per second = 100,000 * 1000 / 86400 = 11500 days MTBF
Writing 1M per second = 100,000 / 86400 = 11.5 days MTBF

Details at: http://cfd.info-for.us/mtbf.html

Re: cf wear levelling strategy
tech@ide-cf.info-for.us (Tech Support for IDE-CF) wrote in message
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PS: This is assuming that the sector translation table is stored in EEPROM,
which has a typical life time of 1,000,000.  So, the sector translation table
will wear out long before the actual sectors.

i.e.: 1,000,000 / 86400 = 115 days MTBF

Quoted text here. Click to load it

In conclusion: Don't bet on wear leveling.  Mount CF read-only.

Updated details at:  http://cfd.info-for.us/mtbf.html

Re: cf wear levelling strategy
Did they forget the FAT updates in the calculations ? I suppose this
always is a "one sector rewrite" and thus a "worst case" operation. As
there usually are two copies of the FAT the worst case is worse by
factor three. Of course the OS caching the FAT will help a lot, but
results in increased power fail problems.

Is there any word about the infamous power off problem in the docs ?

-Michael

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