UFFS: Ultra-low-cost Flash File System
Project: http://uffs.sf.net/
Blog: http://all-about-uffs.blogspot.com/
Q/A: http://groups.google.com/group/uffs/
Author: Ricky Zheng <ricky_gz_zheng@yahoo.co.nz>
INTRODUCTION
------------
UFFS is a nand flash file system designed for embedded system.
UFFS have some unique and advanced features:
* Low cost: e.g. it needs only 41K bytes RAM for 64MB NAND flash (page size 2048).
* Fast booting: it reads only a few spares from each block, typically
mounting a fully filled file system (Gbits) within one second.
* Superb Reliability:
- The file system is designed for the embedded system which may
frequently lost power/reset without care.
- Journal file system, the file system will automatically rollback
to the last state when lost power on the middle of flash programing.
- When 'write' return without error, the data is guarenteed been
saved on flash.
* Fast file create/read/write/seek.
* Bad-block tolerant, ECC enable and good ware-leveling.
* There is no garbage collection needed for UFFS.
* Support multiple NAND flash class in one system.
* Support bare flash hardware, no operating system needed.
* Support static memory allocation (works without 'malloc').
* Fully simulated on PC (Windows/Linux) platform.
Disadvantage:
* space inefficency for small files: UFFS use at least one
'block'(the minial erase unit for NAND flash, e.g. 16K ) for a file.
* maximum supported blocks: 2^16 = 65535
Memory consuming example:
For page size = 512:
[VARY]Tree nodes: 16 * total_blocks
[CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(512)) = 5.4K
[CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
Example 1: 128M bytes NAND, 8192 blocks, total memory cost:
(16 * 8192)128K + 5.4K + 4.6K = 138K bytes.
Example 2: 32M Bytes NAND, 2048 blocks, total memory cost:
(16 * 2048)32K + 5.4K + 4.6K = 42K bytes.
Example 3: 16M bytes NAND, 1024 blocks, total memory cost:
(16 * 1024)16K + 5.4K + 4.6K = 26K bytes.
For page size = 2048:
[VARY]Tree nodes: 16 * total_blocks
[CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(2048)) = 20.4K
[CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
Example 1: 512M bytes NAND, 8192 blocks, total memory cost:
(16 * 8192)128K + 20.4K + 4.6K = 153K bytes.
Example 2: 128M Bytes NAND, 2048 blocks, total memory cost:
(16 * 2048)32K + 20.4K + 4.6K = 57K bytes.
Example 3: 64M bytes NAND, 1024 blocks, total memory cost:
(16 * 1024)16K + 20.4K + 4.6K = 41K bytes.
BUILD SIMULATOR REQUIREMENT
---------------------------
From V1.2.0, build uffs simulator requires 'cmake'.
'cmake' can be downloaded from: http://www.cmake.org/
or, under Debian/Ubuntu:
sudo apt-get install cmake
BUILD SIMULATOR ON LINUX
------------------------
1) create a 'build' dir along with uffs source dir, for example:
/+
+--build/
+--uffs-1.2.0/
|
2) create Makefiles and build:
cd build
cmake ../uffs-1.2.0
make
5) run simulator (interactive mode):
src/utils/mkuffs
BUILD SIMULATOR ON WINDOWS
--------------------------
1) create a 'build' dir along with uffs source dir,
/+
+--build/
+--uffs-1.2.0/
|
2) Create VC project files:
cd build
cmake ../uffs-1.2.0
3) Open uffs.dsw (or uffs.sln for VC > 6 ), compile & run.
LATEST SOURCE CODE
------------------
You can get the latest source code from git repository:
git clone git://uffs.git.sourceforge.net/gitroot/uffs/uffs
CURRENT STATUS
--------------
UFFS 0.1.x is a working version on PC simulator, also has been ported to
uBase embedded OS as a 'real world' product for thousands of copies,
it works fine so far.
UFFS 0.2.0 implementes full directory.
UFFS 1.0.0 is the first stable release at sf.net.
UFFS 1.1.0: support NAND flash with large page size (up to 2K).
UFFS 1.1.1: bug fixes. a tool for making uffs disk image.
UFFS 1.1.2: bug fixes. add more Flash Class. change Licence from GNU GPLv2 to GNU LGPLv2
UFFS 1.2.0:
- eliminate 'current path' and relatives. Now you should use absolute path in all
uffs APIs. For dir, the fullname should end with '/'.
- allow using static memory allocation, 'malloc' is no longer needed.
- using cmake for building simulator.
- bug fixes & minor changes.
UFFS 1.2.1:
- improve bad block management
- bug fixes
- change Licence to modified GNU GPLv2.
UFFS 1.3.0:
- improved flash interface
- support hardware ECC
- support user defined spare layout (for customized NAND flash controller)
- support 4K page size
- no partial page program required, support MLC NAND flash
- reduced buffer flushes by grouping buffers
- structual improvments and bug fixes
UFFS v1.3.1:
- Tidy up three memory allocators: static, native and system.
- Fix bugs in flash interface example.
- Fix memory allocation bugs when using static memory allocator.
- Add flash driver interface 'WriteFullPage()'.
- Fix compilation errors for BlackFin DSP compiler.
UFFS v1.3.2:
- Add POSIX like file system APIs.
- Bug fixes.
LICENCE
-------
From v1.2.1, UFFS is released under a midified GNU GPLv2. (the same as eCos Licence)
The full licence text can be found in the header of source files:
UFFS is free software; you can redistribute it and/or modify it under
the GNU Library General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any
later version.
UFFS is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
or GNU Library General Public License, as applicable, for more details.
You should have received a copy of the GNU General Public License
and GNU Library General Public License along with UFFS; if not, write
to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
As a special exception, if other files instantiate templates or use
macros or inline functions from this file, or you compile this file
and link it with other works to produce a work based on this file,
this file does not by itself cause the resulting work to be covered
by the GNU General Public License. However the source code for this
file must still be made available in accordance with section (3) of
the GNU General Public License v2.
This exception does not invalidate any other reasons why a work based
on this file might be covered by the GNU General Public License.
ACKNOWLEDGMENT
---------------
Special thanks for your contributions to:
(list in no particular order)
* Chen Jun <chj@nlscan.com>
* Michail <digiolog@mail.ru>
* Sjpu <sjpu@163.com>
* RobertGray <xennex@hotmail.com>
* Dongbo <dongbo@ftsafe.com>
* Cag <seucag@hotmail.com>
* Sergey <s_sazonov@m2m-t.ru>
* Chris Conrad <chris.conrad@halliburton.com>
* Vladimir <decoder@rambler.ru>
* Thien Pham <thienpham2008@yahoo.com>
* Emmanuel Blot <eblot.ml@gmail.com>
* Michael <yowong2@gmail.com>
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