Re: Have ext3 on SanDisk CF but can't disable write-back caching as kernel instructs

From: Bill Pringlemeir (spam_account_at_sympatico.ca)
Date: 07/18/03 

Date: 17 Jul 2003 22:40:35 -0400

On 17 Jul 2003, me@linnix.com wrote:

> Are they willing to put it in writing?
>
> CFs are rated for approx. 100,000 write cycles. It will last
> thousands of years only if you write once a day.

Flash often has write/erase cycles of 100,000 [although many newer
devices are rated at 1,000,000]. However, that is a single byte in a
single sector. With wear leveling, you *should* write to all sectors
on a flash equally. 256 sectors will magnify the values and if you
also account for some sort of "bad sector" marking you can extend the
life further as the write cycles are typically the minimum. The
failure mode of flash is not immediate either. It just takes longer
and longer for the tunneling to work... meaning longer and longer
programming time.

When I calculated the effects of wear leveling on flash, it extended
the life from about a year (at one write per second) to over ten
years. One thousand sounds a bit optimistic, but not impossible.

fwiw,
Bill Pringlemeir. 

-- 
Feynman on QED: I don't understand it.  Nobody does.

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