I'm surprised that searching for "UBIFS" doesn't return any (maemo.org) or few (ITT) results.

What I read about it:

• It's a file system designed to outperform and replace JFFS2 on flash media.
• It's faster than JFFS2.
• The driving force behind it is Nokia.
• It's supposed to be in the kernel as of 2.6.27 (so it's ready for production now).

Wouldn't all of this suggest that we might see UBIFS instead of JFFS2 in the near future on the tablets? From what I read it would improve performance quite a bit.

Any comments?

Kerneltrap article on UBIFS from 28 March 2008.

I agree with all your comments. Did I hear someone whispering OS2009?

Its been pushed to Linus for 2.6.27 which is good. As far as I know the main area it will improve performance is not going to help the n800/n810 devices. It helps most when mounting large rootfs(es) on the internal flash (not the /media/mmcx usb sd(hc) stuff). So its major advantage will be on new devices with larger internal flash.

Actually I thought of it *only* as a file system for the internal rootfs. SD/MMC are usually FAT for compatibility reasons (say hello to Windows users!), right? But the internal flash (rootfs, initfs) is JFFS2. Only this would benefit from a change to UBIFS.

(Although I wonder: Wouldn't that mean we'd have to re-flash again? They can't distribute a new file-sytem for the whole internal flash the same way the update packages...? Or would it be just for the "N900"?)

One can mount ext2/ext3 on Windows read/write... [1]

It's clear from the article that while the filesystem is a future replacement for jffs2 it probably wasn't nearly ready in time for Diablo, let alone Chinook both of which use 2.6.21 IIRC.

I would bet it's on the table for the next major revision unless there are issues with the stability. Jffs, while having it's issues, is a time tested flash filesystem driver.

Will it be in Maemo5? Any information on this from Berlin?

Thanks for the kerneltrap link.
BTW it mentions that UBIFS has been tested on the N810.

Indeed.

UBIFS requires Linux kernel 2.6.22 though because it uses UBI which was included in that .22. They also tested it on OLPC, but first on N810. At least that was the case begin of april (interesting post by developer). It cannot be used on N800 because its designed for flash without FTL. We don't know what later versions will of N-series + Linux bring, but if people want N900 with 2 SD cards and no real flash w/o FTL, UBIFS is not useful. Because the WiFi driver is now open source, later versions than 2.6.21 can be used for N810 sooner or later. This opens doors for HE, and perhaps indeed UBIFS.

http://www.linux-mtd.infradead.org/doc/ubifs.html good page with intro for UBIFS.

Huh? IMO there is no difference between 770, N800 and N810 in this regard. All of them use raw NAND access without any translation layer.
Well I guess someone could even backport UBIFS from 2.6.22 to 2.6.21 to have it running on current devices with Diablo. Maybe such backport already exists. It would need some initfs hacking and fulll rootfs reflash of course.

It is easier to just boot from SD and forget about jffs2 (or UBIFS), though.

I wonder about UBIFS future in the light of eMMC chips (like the 2GB MoviNAND one in N810) which provide transparent block devices without any need for messing with raw NAND.

Still, plain non-managed NAND chips are cheaper and perhaps UBIFS can work better and give better control than any FTL hidden inside managed NAND chip so there is future for UBIFS too.

I wonder whether N900 will ditch internal OneNAND for bigger eMMC chip or ditch eMMC for large UBIFS volume. In any way 256MB jffs2 is quite limiting today.