Re: [Yaffs] Products shipping YAFFS ??

On Friday 02 March 2007 10:59, Johnson, Charles F wrote:
> I'm trying to understand the relative merits of JFFS2 vs YAFFS2. The
> response on the YAFFS mailing list is quite positive as far as leading
> me to believe that there are actual products shipping.

At a technical level, it is very difficult to make x vs y comparisons because
there are many factors involved which manifest differently on different
systems therefore mileage will vary. But, as a general rule of thumb, the
following might help:
1) YAFFS uses less run-time RAM to hold its state so YAFFS scales better than
JFFS2. There are quite a few systems using large NAND arrays (the largest
partitions I know of are around the 6Gbyte mark).

2) YAFFS garbage collection is simpler and faster typically making for better
performance under hard writing.

3) YAFFS uses a whole page per file for headers, and does not provide
compression. This means that JFFS2 is probably a better fit to small
partitions. The flip side though is that a lot of data (eg. MP3) does not
compress very well and enabling compression really hurts performance.

4) While YAFFS has been used on NOR, it does not fit that well (because YAFFS
does not use erase suspend). Thus if you're using smaller NAND partitions and
using jffs2 on NOR, then a jffs2-only solution is very appealing.

All the above can generally boil down to:
If you're using less than about 64MB the pain vs gain might play in favour of
JFFS2. As you increase partition size, YAFFS makes more and more sense.

YMMV!

-- CHarles



>
>
> Charles Johnson
> Ultra-Mobility Group
> Platform Software Engineering
> Intel Corporation
> charles.f.johnson@intel.com
>
>
> -----Original Message-----
> From: Charles Manning [mailto:manningc2@actrix.gen.nz]
> Sent: Thursday, March 01, 2007 1:59 PM
> To: yaffs@lists.aleph1.co.uk
> Cc: Johnson, Charles F
> Subject: Re: [Yaffs] Products shipping YAFFS ??
>
> On Friday 02 March 2007 10:24, Johnson, Charles F wrote:
> > I'm new to YAFFS. Is there a list of products that are known to
> > shipping YAFFS ?? I couldn't find anything in the archives.
>
> Hi Charles
>
> There is no hard list. If you look on the yaffs list, you can figure out
> a bit
> by looking at email addresses.
>
> I know of many products shipping with YAFFS, but I am unable to give out
> those
> sorts of detail without permission.
>
> These products range through cell phones, PDAs, consumer (TV,
> entertainment,
> MP3), aerospace, vehicle navigation, point of sale,....
>
> Most people are using YAFFS with Linux and many have used pre-configured
>
> bundles (such as produced by MontaVista). As such, I often don't even
> hear
> about most usage. Sometimes the first I hear of a YAFFS usage is when a
> manufacturer asks for some details about how to program the NAND chips.
> Sometimes the first I find out is when I hear from someone who knows me
> that
> has fiddled with an embedded device and seen that it runs a yaffs
> partition.
>
> There has been a huge uptake of YAFFS in Linux cell phones (particularly
> in
> Korea).
>
> Almost all YAFFS development has been funded, mainly by people wanting
> to add
> some new feature to YAFFS.
>
> So sorry, no concrete data :-).
>
> -- Charles
>
>
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