Re: safe flash filesystem

[Abraham vd Merwe <abraham@2d3d.co.za>]

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Hi Russ!

> > Yes, this is something in the lines I was thinking of. But what complicates
> > things is if you start taking things like avoiding damaged blocks into
> > account, wear levelling (this is fairly easy to solve) and keeping the flash
> > unfragmented.
> > 
> if you only eraseblocks when you need to, you always have at least N-1 
> eraseblocks of pevious data, (where N is the number of eraseblocks 
> used). A CRC can be done after the store to see if the node written is 
> ok, if not, write it again (in the next node). since its a small amount 
> of data (maybe 4-8k) and written linearly, wear leveling and 
> fragmentation is not a problem. Lets say 4 parameter blocks of 16k a 
> peice are used, that would be 1 erase cycle per 8 configs written, this 
> would allow 800,000 configs to be written on standard flash. If a config 
> was written at a rate of once an hour, it would last 93 years. If it 
> were on 2 128k standard blocks, then you wolud have 3.2M configs 
> written, which at the same rate, would last about 332 years. Remember, 
> you are only performing an erase cycle after a block fills up, not for 
> every write.

True, but once the flash fills up you have to start moving things around to
erase entire blocks and then the whole 4k-8k thing doesn't hold anymore.

But anyhow, like you said, it's not the most complicated thing in the world.

-- 

Regards
 Abraham

You don't have to know how the computer works, just how to work the computer.

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 Abraham vd Merwe - 2d3D, Inc.

 Device Driver Development, Outsourcing, Embedded Systems

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