Re: [gentoo-embedded] file system question

[Nebojša Ćosić]

> 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