Reliability of FLASH data storage

Jason Gunthorpe jgg at
Sat Nov 27 20:26:11 EST 1999

On Fri, 26 Nov 1999, David Woodhouse wrote:

> What I really want to do is a filesystem directly on the flash - none of this 
> 'pretend it's a block device' stuff.
> Jason, how's FFS2 coming along? Is it possible to make it POSIX-compliant 
> without a hack as evil as UMSDOS?

I'm afraid I haven't been working on that lately, back at school and no
time for it :< 

But yes, FFS2 directly on flash largely addresses this problem. There are
still some possible problems but those largely reduce down to requiring a
quick 'fsck' type pass on mount. Basicalyl with FFS2 the worst thing that
can happen is that the filesystem looses track of a block, ie you allocate
something but never link it into the filesystem strutures, this reduces
the available space in the filesystem, but does not harm the data or the
filesystem itself.

I think journaling on flash is really a rather overkill, due to the nature
of the device you can do built in journaling cheaply like FFS2 does and
not pay a space premium for a journal.


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