Update with current yaffs added below
>> Hello everyone,
>>
>> Question #1: I was told that UBIFS is better than Yaffs2, is that
>> true? What are pros and cons?
>> Question #2: It was said that Android 2.1 cannot use Yaffs2, is that
>> true? If so, why?
>>
>> BR
>> Russell
>>
>>
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>>
>
> I recently ported ubifs to a balloon3 development system and wish to
> report some findings.
>
> The kernel is 2.6.34 with nand write verify disabled due to subpage
> write problems exposed by ubifs, using yaffs checkout 2009-09-10 and
> using default ubifs lzo compression.
>
> 1) The first test was decompressing a 41MB tgz unconfigured rootfs from
> a pen drive into a nand partition. This was done using tar -xzf
> ../sda1/embdebianrootstrap.tgz from the empty mounted nand partition.
>
> yaffs2: 5:20
> ubifs: 1:38
>
I retried with the latest yaffs2 checkout. Decompression was 5:58.

> 2) dpkg --configure -a after chrooting into the new rootfs partition
>
> yaffs2: 6:25
> ubifs: 5:01
>
configure took 6:03

Nick
> 3) booting from bootldr prompt into the newly created rootfs cleanly
> unmounted. This including kernel reading-decomprerssing-initialisation
> time of about 5 secs.
>
> yaffs2: 0:28
> ubifs: 0:23
>
> 4) rebooting into cleanly unmounted rootfs
>
> yaffs2: 0:28
> ubifs: 0:23
>
> 5) rebooting into power yanked rootfs (no writes)
>
> yaffs2: 0:36
> ubifs: 0:24
>
> 6) single write to small file then reboot via power yank
>
> yaffs2: 0:36
> ubifs: 0:24
>
> Under ubifs, df reported 69MB of filesystem space used representing
> 126MB of du reported data. The increased boot/read speed might be
> accounted for by the fewer nand reads (software ecc) needed due to data
> compression.
>
> This leaves the tgz decompression figures to be explained as the
> difference is remarkable. Copying the tgz to /dev/null took 44 seconds
> of reading from a usb 1 mounted memory stick reducing the residual
> timings to
> yaffs2: 4:36 vs ubifs: 0:54.
>
> These figures take no account of newer yaffs2 speed improvements, no
> account of the degraded power security of cached writes and no account
> of reliability issues surrounding not verifying nand writes. Verifying
> nand writes is ok under ubifs but the header offsets must be page (not
> sub-page) aligned until sub-page verifies are fixed in mtd. Using page
> aligned headers which requires that userland ubifs utils must have
> knowledge of the underlying nand architecture - ugh.
>
> My impression of running our applications on ubifs is that the write
> speed and boot speed (especially without a clean unmount) is faster but
> without the numbers to back it up this is only an impression. Installing
> packages using dpkg (which makes many writes/moves) also seems much
> faster. Overall reliability is far too early to judge.
>
> If someone can tell me how to do a git checkout without using long
> unmemorable nubers I could redo this with a more modern yaffs2.
>
> Nick Bane
>
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