Reliability of NAND JFFS2 vs YAFFS for Embedded Systems

Reliability of NAND JFFS2 vs YAFFS for Embedded Systems

[Chris]

Hi all,

I was hoping that anyone who had some experience with JFFS2 and YAFFS NAND 
devices could give a good idea of the reliability of both filesystems.  I 
have attempted the JFFS2 filesystem on Toshiba NAND TC58256AFT with some 
success but have encountered CRC errors when rebooting or interrupting 
power 
during writing.

I am considering moving to the YAFFS filesystem due to reliablity 
concerns, 
but I am also wondering if YAFFS will have its own can of worms.  I would 
like to have reliability, performance and space but reliability is the 
most 
important concern. 

Does anyone have experience with testing reliability of both 
configurations?  
If so what were the resutls?

Should I change to YAFFS?  Why?

Or should I stay with JFFS2?  Why?

Thanks,

Chris Sperandeo

Re: Reliability of NAND JFFS2 vs YAFFS for Embedded Systems

[David Woodhouse]

On Fri, 2003-06-13 at 01:05, Chris wrote:
> I was hoping that anyone who had some experience with JFFS2 and YAFFS NAND 
> devices could give a good idea of the reliability of both filesystems.  I 
> have attempted the JFFS2 filesystem on Toshiba NAND TC58256AFT with some 
> success but have encountered CRC errors when rebooting or interrupting 
> power during writing.

Yes, of course you do. That's what the CRC is _for_ -- to detect nodes
which were partially-written due to such circumstances. 

Do you actually see corruption or are you just complaining about the
verbosity of the file system?

> I am considering moving to the YAFFS filesystem due to reliablity 
> concerns, but I am also wondering if YAFFS will have its own can of 
> worms.  I would like to have reliability, performance and space but 
> reliability is the most important concern. 
> 
> Does anyone have experience with testing reliability of both 
> configurations?  
> If so what were the resutls?

There's been powerfail testing done on JFFS2 on NOR; not yet for NAND
and there are some known corner cases which need sorting out before I
really undertake that. 

-- 
dwmw2

Re: Reliability of NAND JFFS2 vs YAFFS for Embedded Systems

[Thomas Gleixner]

On Friday 13 June 2003 08:02, David Woodhouse wrote:
> On Fri, 2003-06-13 at 01:05, Chris wrote:
> > I am considering moving to the YAFFS filesystem due to reliablity
> > concerns, but I am also wondering if YAFFS will have its own can of
> > worms.  I would like to have reliability, performance and space but
> > reliability is the most important concern.
> >
> > Does anyone have experience with testing reliability of both
> > configurations?
> > If so what were the resutls?
>
> There's been powerfail testing done on JFFS2 on NOR; not yet for NAND
> and there are some known corner cases which need sorting out before I
> really undertake that.

I have done intensive powerfail testing on NAND. I have no problem with JFFS2 
and YAFFS. I think both are reliable and have their (dis)advantages.

Both filesystems have invalid files on it, if the powerfail occures during a 
file write. That's normal behaviour. This would be the same on your harddisk 
or any other medium.

I have never seen a serious fs corruption neither on JFFS2 nor on YAFFS, 
except for some development phases, when the code was buggy. That's normal 
for work in progress too.

The only unsolved problem for JFFS2 on NAND at the moment is a writebuffer 
flush failure. This has hit me once during a log term test, where a sector 
went bad after > 1.200.000 erase cycles. But this did not corrupt the hole 
filesystem. It was just the last written file, which was lost. It should be 
not too hard to fix that at least, if somebody has enough time or someone 
does a little sponsoring for that :)

-- 
Thomas
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