flash device selection

Jan 27, 2005 2 Replies
B

I'm trying to decide on a flash device and filesystem combination for an embedded device. My concerns are:


- Wear leveling Does jffs2 wear level across partitions, or just within a partition? Is the M-Systems hardware leveling controller worth a damn? Is it preferable to using jffs2?


- log data How to structure disk layout best to be able to get log data while not significantly shortening the flash life.


- cost What's the cheapest device I can get away with.



I need 1-2 GB, almost everything is static, except for log data. I plan on having a log on/off switch, but I want to be able to log anomalous events by default.



Thanks, Bruce


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L

an

Wear leveling is usually done in the flash controller, regardless of the file system.

not

If hardware allows it, use a separate (small SLC flash) for log and everything else read-only (bigger MLC).

Compact Flash is cheapest. Less than $200 for 2G.

plan

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M

That's a very bad idea. If the file system does not care about wear leveling and keeps rewriting the same few bytes, the lower level wear leveling uses up the spare blocks much faster then when using a flash-aware file system like jff.

-Michael

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