Re: RAM persistence

Le Wed, 20 Jun 2001 13:43:17 -0500
Kevin Holbrook <holbrook_at_metrowerks.com> ecrivit a Familiar
<familiar_at_handhelds.org> :

> Sorry for asking what is probably a very dumb question,
> but are items written to a ramfs supposed to be persistent?

Nope. In case of powerfailure, you lose everything. Turning it off by
pushing the button is not considered powerfailure. Reset and On/Off switch
IS ;)

>
> Is this equivalent to the standard RAM disks on Linux or
> is this a specialized filesystem driver?

I guess the ramdisk is the closest match.

>
> I was wondering how items were written to flash RAM
> to be persistent.

I think it's the purpose of the jffs, which means, I guess : Journaling
Flash FileSystem

How it comes to be persistent ?

The answer is pretty staightforward :

1. Use of a journaling filesystem to save as often as possible every
changes
2. jffs driver has, builtin, the flashing code, so that it continuously
(sort of) flashes changes to the ROM

Maybe it's not that simple, and maybe I'm completely mistaken, but I think
it's the thing to do (my own opinion, and I'm absolutely not part of the
development team : I'm not gifted enuff for it ;) )

>
> I was also wondering why I only have access to 16Mb of
> the 64MB on the iPaq 3670 as well via the ramfs.

The system needs RAM to work properly. I've been asking myself the same
question (though I only have 32Mb on my H3630), but it's pretty obvious
that an OS can't work without RAM.

Hope I'm not entirely wrong ...

cyaz

A.

-- 
Arnault Claden
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