Powerfail-tests and jffs2-sync-mount

[Schlaegl Manfred jun.]

Hi!

Am Freitag, den 07.03.2008, 08:10 +0200 schrieb Artem Bityutskiy:
> On Thu, 2008-03-06 at 17:41 +0100, Schlägl Manfred jun. wrote:
> > Hi!
> > 
> > I did some powerfail-testing of jffs2. 
> > 
> > Short overview (Contact me for details):
> > Arch: ARM926EJ-S with 40MB rw jffs2 part on Samsung NAND-Flash
> > Kernel: linux-2.6.12 (a little bit out of date, i know ;-))
> > Test: 
> >  * Target-Loop
> >    * filesystem-consistency:
> >      * create dir
> >      * copy data(> eraseblock-size) to new file
> >      * delete a file
> >    * file-consistency:
> >      * logfile on jffs-part (simply appending text with echo)
> >  * External random-time reset:
> >    * external uC
> >    * generates reset every 120+rand(0..30) seconds
> >  * Run until no more space on filesystem
> > Results:
> >  * test with sync-mounted jffs2 (mount -o sync):
> >    * duration 4:40 hours
> >    * 131 generated resets
> >    * consistent FS
> >    * consistent logfile
> >  * test with async mounted jffs2:
> >    * duration 4:10 hours
> >    * 118 generated resets
> >    * consistent FS
> >    * corrupted logfile (bad-chars, etc.)
> > 
> > Now my question: Are there any non-obvious disadvantages, mounting jffs2
> > synchronal, except lower speed and a little(depends on usage) decreased
> > flash-life-time (wear-out), or is this anyway the default approach?
> 
> My understanding of the things is that this should not really matter. I
> thought if you have some corruption in asynchronous mode, you should
> have them in synchronous too, may its worth trying more synchronous mode
> testing?
> 
I thought it's a matter of file-buffers between the file-operations and
jffs2, but these buffer should be flushed on close of the file, so there
should be no problem with echo.
I think i've to take a look on vfs, perhaps there is some buffering, or
(even worst) some reodering of actions.

Currently i've to do some other tests (bootloader bad-block-handling).
After that I will work on some methodes to keep different
files-types(config-files, log-files, ...) conistent in case of
powerfail. So I will do some further tests on saturday or thursday.

Best regards,
        Manfred Schlaegl