UBIFS

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Introduction

UBIFS is a filesystem that works on top of UBI volumes

UBIFS vs. YAFFS2 comparisons for 2.6.31.1

First, see our Flash_Filesystem_Benchmarks for more recent benchmarks.

Hardware: MIPS, 403MHz CPU, 1GB Nand Flash

IOZone results: 4M, 8M & 16M file sizes in 980MB partition.

  • mount time
    • "1st mount" : time for mounting just after "flash_eraseall".
    • "Empty" : time for mounting after "1st mount".(there's no files in partition)
    • "Full" : time for mounting after creating files util the partition is full.(file size is random.)
    • "Ubiattach" time for attaching 980MB partition into the ubi layer using ubiattach util.
Ubiattach Ubifs Yaffs2
1st mount 2.59 sec 0.17 sec 2.25 sec
Empty 2.57 sec 0.11 sec 0.03 sec
Full 2.63 sec 0.16 sec 0.80 sec


  • IOZone results
UBIFS compared to YAFFS2 (file size = 4MB)
4M write rewrite read reread r.read r.write b.read r.rewrite s.read fwrite frewrite fread freread
yaffs2 1538 1527 296962 297696 297825 1521 296876 1526 295164 1536 1524 297436 299021
ubifs 19913 20989 298346 297631 299809 20968 298368 20181 299458 20471 20962 297371 297760
ubifs/yaffs2 12.95 13.75 1.00 1.00 1.01 13.79 1.01 13.22 1.01 13.33 13.75 1.00 1.00
UBIFS compared to YAFFS2 (file size = 16MB)
16M write rewrite read reread r.read r.write b.read r.rewrite s.read fwrite frewrite fread freread
yaffs2 1538 1523 297199 298525 298896 1528 298433 1525 298847 1538 1525 299661 300656
ubifs 20501 20656 298272 299109 299032 20521 298417 20710 298923 20448 20521 298259 299267
ubifs/yaffs2 13.33 13.56 1.00 1.00 1.00 13.43 1.00 13.58 1.00 13.30 13.46 1.00 1.00
UBIFS compared to YAFFS2 (file size = 32MB)
32M write rewrite read reread r.read r.write b.read r.rewrite s.read fwrite frewrite fread freread
yaffs2 1539 1525 296537 297204 297253 1527 297177 1527 296583 1531 1523 296537 297463
ubifs 20474 20611 296765 297490 297334 20659 296972 38416 297371 19068 20059 296618 296658
ubifs/yaffs2 13.30 13.52 1.00 1.00 1.00 13.53 1.00 25.16 1.00 12.45 13.17 1.00 1.00

Creating UBI Image

This is easiest to do, if you have access to the device and can run ubinfo and dmesg, otherwise you'll need to determine the volume size, Logical Erase Block size, etc by other means. UBI has some block overhead, which I found documentation inconsistent with my particular application, so your results may very. If your device is one UBI image for the entire NAND, this should be easier, and could probably be determined by just mounting a copy of the UBI image from the device if available.

To create the image from a rootfs you've built first you need to create the ubi.ini file, that describes your ubi image. Create a regular text file, ubi.ini, example contents, for more info run ubinize -h:

[ubi_rfs]
mode=ubi
image=ubifs.img
vol_id=0
vol_size=87349248
vol_type=dynamic
vol_name=ubi_rfs
vol_alignment=1
vol_flags=autoresize

Next you'll run the commands that actually build it. Here ubi.ini is the file you just created, ubifs.img is a temp file you can delete once you are done, and your_erootfs.ubi is the name of the rootfs image that will be created.

sudo /usr/sbin/mkfs.ubifs -m 2048 -e 129024 -c 677 -r /path/to/rootfs ubifs.img
sudo /usr/sbin/ubinize -o your_erootfs.ubi -p 131072 -m 2048 -s 512 -O 512 ubi.ini

To determine these and the ubi.ini file settings, use ubinfo -a and dmesg on the device if possible, which both give plenty of information about the values needed. The size and vol_name are listed under "Present volumes" when you run ubinfo -a on the device. The second half of that particular ubi device's description. While the NAND description's PEB, LEB etc are in dmesg.

mkfs.ubifs

  • -m - Minimum I/O unit size.
  • -e - Logical Erase Block (LEB) size.
  • -c - Max LEB count. (vol_size/LEB)
  • -r - Path to root filesystem.
  • ubifs.img - Temporary image file.

ubinize

  • -o - Output file.
  • -p - Physical Erase Block (PEB) size.
  • -m - Minimum I/O unit size.
  • -s - Minimum I/O size for UBI headers, eg. sub-page size.
  • -O - VID header offset from start of PEB.
  • ubi.ini - UBI image configuration file.