Re: [ts-7000] Re: Microdrive / Type II CF?

["Don W. Carr" <>]

Ok, all very interesting. I will think about which file system to use.
Even if it were 3 x more writes with ext3 (which I find hard to believe
since it would kill performance), it would be good for 16,000 years
instead of 50,000 years, assuming that it takes 1/2 year to fill the
card, 100,000 writes maximum.

Don.

On 6/2/06, Jesse Off <> wrote:

> In general any standard journalling file system (ext3, xfs, reiser)
is bad
> with flash because they do 3 device writes per software write
operation...
>
>  - write to journal
>  - do real data update
>  - rewrite journal record
>
> As you can see the journal area gets a lot of write hits too,
hopefully
> the wear levelling will help. But remember never use a journalling
> filesystem with a floppy :-)

Exactly.  Though I believe EXT3 only journals metadata block writes so
maybe its not too bad.  If it truly was 3 writes for every real write
we should be able to see that fairly obviously as a 3x slower file
write speed though it may be a bit more complicated than that.

A pet project I've had is to plug into the Linux block driver layer
and actually do some accounting of number of block writes to some user
accessible file in /proc.  You could watch the flash write "load" by
seeing how many writes accumulate during some sample period and
therefore make predictions as to how long the flash should last at
that write rate and optimize accordingly.  You could even make
objective comparisons between EXT2 and EXT3 to see if the extra
stability of EXT3 outweighs the difference in flash lifetime on a
project by project basis.

//Jesse Off

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Dr. Don W. Carr
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