> -----Original Message-----
> From: yaffs-bounces@lists.aleph1.co.uk [mailto:yaffs-
> bounces@lists.aleph1.co.uk] On Behalf Of Kumar, Venkat
> Sent: Thursday, 17 September 2009 8:56 PM
> To: yaffs@lists.aleph1.co.uk
> Subject: [Yaffs] Significance of Log Structured file system
>
> This may not be very specific to Yaffs but a generic question on Log
> structured flash file systems.
>
...
> If a flash device is handling Wear-leveling & Bad block management,
what
> is the significance of a log structured flash file system?
>
If a FTL(Flash Translation Layer) is able to handle wear-levelling and
bad block management by itself, *perfectly*, and you're not worried
about crash recovery, then there would be no need for log-structured
file systems.
In the real world, FTLs contain significant black-box magic, and aren't
perfect. They would have to be effectively log-structured themselves to
come close, and then you would have the worst of both worlds, with a few
extra problems for good measure! Mount-time scan delay caused by the
log-structure layer, unclean shutdown issues caused by the conventional
filesystem, and fragmentation/slowdown issues because both halves have
differing ideas of where the free space is... (DISCARD might help there,
though.)
J
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