Re: [gentoo-embedded] file system question

[David Relson <relson@osagesoftware.com>]

On Wed, 31 Mar 2010 11:26:49 +0200
Nebojša Ćosić wrote:

> > G'day,
> > 
> > I'm porting the software for an embedded medical device from DOS to
> > Linux and am wondering which file systems are appropriate and which
> > are not.  The device's mass storage is a Disk-on-Module solid state
> > flash drive.  Data is presently written at approx 100 bytes every
> > 30 seconds but that might change to 100 bytes every second.  The
> > device has a watchdog (recently activated) and during today's
> > session it was triggered and wiped out my file system.
> > 
> > Anybody have recommendations on which file system to use and the
> > appropriate settings?
> > 
> > Anybody have suggested readings so I can educate myself?
> > 
> > Thank you.
> > 
> > David
> > 
> After having problems with EMC and usb storage, I finally fixed the
> problem with following solution:
> - data storage, in my case usb stick, has at least 2 partitions
> - second partition is without file system. It is divided in a number
> of slots, each large enough to store all of my data
> - all work is performed on data stored on ram disk
> - periodically (triggered by time and/or data change), I compress ram
>   disk and dump it in a next slot on unformatted partition
> I have a small battery, which I use to do one final dump at shutdown
> time.
> On startup, I go through all of the slots in second partition,
> searching for latest uncorrupt data, and use this to populate ram
> disk. If you can live with some data loss, you don't even need
> battery backup. No matter wear leveling implementation on your
> storage, this solution works optimally.
> It works even on your directly accessible flash storage.
> Since there is no real file system on partition, there is no need for
> it's recovery - besides searching for latest and greatest set of data
> on startup
> And it is implemented as a ash script, using tar and gzip, so your
> data is actually better verified than on normal file system (the
> usual one do not actually checksum data. I don't consider jffs2 to be
> "the usual filesystem":)
> Nebojša

Wow!  That's a robust solution!