Re: JFFS2 mount time

Gareth Bult (Encryptec)
2004-12-20T17:12:26Z

On Mon, 2004-12-20 at 10:34 -0600, Josh Boyer wrote:
> Ok, that's why I said "most". And if your El Cheapo hardware has built
> in wear leveling, then doing wear leveling on top of that is always
> questionable. It might not make things worse, but it's probably not
> very efficient.

Mmm, if the USB flash micro-controllers have build-in wear levelling,
they'd be quite something .. (!)

> Now if you have El Super Cheapo hardware that explicitly states you need
> to do wear leveling, that's a different story ;).

Here's a quote from a "Kingston" advert;

"Controllers automatically lock out bad memory cells and move the data
to avoid corruption. Controllers also automatically distribute write
cycles across the flash cells to extend the life of the flash memory
card"

What this means exactly in real terms .. [?]
(for example, do you lose some of your key to a bad block table, if so
how much ???)

Here's a bit from "Verbatim";

"For ultra-reliability, Verbatim’s new Store ‘n’ Go Pro drives feature
an on-board 32 bit ARM-7 microprocessor that manages I/O operations and
many of the drive’s technical features. An advanced wear-leveling
algorithm is used to distribute writes evenly among flash storage cells.
By evenly distributing the writing, Store ‘n’ Go Pro achieves an
unprecedented reliability rating of over one million write/erase cycles.
Advanced Error Detection Code/Error Correction Code furthers the Store
‘n’ Go Pro’s immunity to failure."

Interesting articles / links;
http://www.digitalmediadesigner.com/articles/viewarticle.jsp?id=27727
http://www.techworld.com/features/index.cfm?fuseaction=displayfeature&FeatureID=413

In summary: lots of manufacturers seem to be quoting virtual / physical
block mapping on the fly with integrated wear levelling ... (!)

So maybe wear levelling is out of date at filesystem level ?
The techworld link to the M-Systems chips looks interesting ..

Can anyone with detailed flash experience comment ?

Gareth.

> That's because it was the only removable media for PCs for a long time.
> At least to the non-geeks. I can remember buying spare hard drives and
> carrying those from machine to machine if I needed to do big transfers
> ;).
>
> josh
>