==================================
ϡ
linux-2.6.13-rc3/Documentation/filesystems/ext3.txt 
Ǥ
Ρ JF ץ < http://www.linux.or.jp/JF/ >
  2005/8/1
  Hiroshi.Suzuki < setter at reset dot jp >
  Chie Nakatani  <jeanne at mbox dot kyoto-inet dot or dot jp>
	 Masanori Kobayasi  <zap03216 at nifty dot ne dot jp>
==================================


Ext3 Filesystem

Ext3 ե륷ƥ
===============

ext3 was originally released in September 1999. Written by Stephen Tweedie
for 2.2 branch, and ported to 2.4 kernels by Peter Braam, Andreas Dilger, 
Andrew Morton, Alexander Viro, Ted Ts'o and Stephen Tweedie.

ext3 ϽΤΤϡ1999ǯ9˥꡼ޤ
Stephen Tweedie ˤꡢ2.2ϤΤ˽񤫤졢
Peter Braam , Andreas Dilger , Andrew Morton , Alexander Viro , 
Ted Ts'o , Stephen Tweedie  ˤꡢ2.4 ͥ˰ܿޤ

ext3 is ext2 filesystem enhanced with journalling capabilities. 

ext3 ϡext2 򥸥㡼ʥ󥰵ǽǶΤǤ

Options

ץ
=======

When mounting an ext3 filesystem, the following option are accepted:
(*) == default

ext3 ե륷ƥޥȻʲΥץ󤬻Ȥޤ
(*) == ǥե

jounal=update		Update the ext3 file system's journal to the 
			current format.

jounal=update		ext3 ե륷ƥΥ㡼ʥ򸽺ߤη˥åץǡȤޤ

journal=inum		When a journal already exists, this option is 
			ignored. Otherwise, it specifies the number of
			the inode which will represent the ext3 file
			system's journal file.

journal=inum		Ǥ˥㡼ʥ뤬ʤ顢Υץ̵뤵ޤ
			ǤʤСext3 ե륷ƥΥ㡼ʥեɽ 
			inode ꤷޤ

noload			Don't load the journal on mounting.

noload			ޥȻ˥㡼ʥɤ߹ޤʤ

data=journal		All data are committed into the journal prior
			to being written into the main file system.

data=journal		ǡϡᥤΥե륷ƥ˽񤭹ˡ
			㡼ʥ˥ߥåȤޤ

data=ordered	(*)	All data are forced directly out to the main file
			system prior to its metadata being committed to
			the journal.

data=ordered	(*)	ǡϡΥ᥿ǡ㡼ʥ˥ߥåȤˡ
			ᥤե륷ƥľܽϤޤ

data=writeback		Data ordering is not preserved, data may be
			written into the main file system after its
			metadata has been committed to the journal.

data=writeback		ǡν¸ޤ
			ǡϡΥ᥿ǡ㡼ʥ˥ߥåȤ줿Ȥˡ
			ᥤե륷ƥ˽񤭹ޤ뤫⤷ޤ

commit=nrsec	(*)	Ext3 can be told to sync all its data and metadata
			every 'nrsec' seconds. The default value is 5 seconds.
			This means that if you lose your power, you will lose,
			as much, the latest 5 seconds of work (your filesystem
			will not be damaged though, thanks to journaling). This
			default value (or any low value) will hurt performance,
			but it's good for data-safety. Setting it to 0 will
			have the same effect than leaving the default 5 sec.
			Setting it to very large values will improve
			performance.

commit=nrsec	(*)	Ext3 ϥǡȥ᥿ǡ'nrsec' ƱǤޤ
			ǥեȤϡ5äǤϡŸڤƤޤä
			Ǹ5ô֤κƤƤޤȤ̣ޤ
			(ե륷ƥϡ㡼ʥ󥰤Τ˲ʤǤ礦)
			Υǥե(ޤϡ꾮) ϡѥեޥ󥹤˱ƶͿޤ
			ǡΰɤʤޤ0 ˤϡǥեȤ5ðʲˤΤƱ
			̤ޤȤƤ礭ͤˤȥѥեޥ󥹤ޤ

barrier=1		This enables/disables barriers. barrier=0 disables it,
			barrier=1 enables it.

barrier=1		Хꥢͭ/̵ˤޤbarrier=0 ̵barrier=1 ͭ

orlov		(*)	This enables the new Orlov block allocator. It's enabled
			by default.

orlov		(*)	Orlov ֥åͭˤޤǥեȤͭǤ

oldalloc		This disables the Orlov block allocator and enables the
			old block allocator. Orlov should have better performance,
			we'd like to get some feedback if it's the contrary for
			you.

oldalloc		Orlov ֥å̵ˤơŤ֥åͭˤޤ
			Orlov ǥѥեޥ󥹤ɤʤϤǤ⤷ո̤ʤ顢Τ餻Ƥ

user_xattr	(*)	Enables POSIX Extended Attributes. It's enabled by
			default, however you need to confifure its support
			(CONFIG_EXT3_FS_XATTR). This is neccesary if you want
			to use POSIX Acces Control Lists support. You can visit
			http://acl.bestbits.at to know more about POSIX Extended
			attributes.

user_xattr	(*)	POSIX ĥ°ͭˤޤǥեȤͭǤ
			ݡ(CONFIG_EXT3_FS_XATTR) Ȥ߹ɬפޤ
			 POSIX ꥹ(POSIX ACL)ݡȤȤʤ顢ɬפǤ
			POSIX ĥ°ξܺ٤ϡhttp://acl.bestbits.at 򸫤Ƥ

nouser_xattr		Disables POSIX Extended Attributes.

nouser_xattr		POSIX ĥ° ̵ˤ롣

acl		(*)	Enables POSIX Access Control Lists support. This is
			enabled by default, however you need to configure
			its support (CONFIG_EXT3_FS_POSIX_ACL). If you want
			to know more about ACLs visit http://acl.bestbits.at

acl		(*)	POSIX ꥹ(POSIX ACL) ݡȤͭˤ롣
			ǥեȤͭǤݡ(CONFIG_EXT3_FS_POSIX_ACL)
			Ȥ߹ɬפޤACL ξܺ٤ϡhttp://acl.bestbits.at
			򸫤Ƥ

noacl			This option disables POSIX Access Control List support.

noacl			POSIX ꥹ(POSIX ACL)  ̵ˤ롣

reservation

noreservation

resize=

bsddf 		(*)	Make 'df' act like BSD.
minixdf			Make 'df' act like Minix.

bsddf 		(*)	'df'  BSD ˻ưˤ롣
minixdf			'df'  Minix ˻ưˤ롣

check=none		Don't do extra checking of bitmaps on mount.
nocheck		

check=none		ޥȤǥӥåȥޥåפ̤ʸ򤷤ʤ
nocheck		

debug			Extra debugging information is sent to syslog.

debug			̤ʥǥХå syslog 롣

errors=remount-ro(*)	Remount the filesystem read-only on an error.
errors=continue		Keep going on a filesystem error.
errors=panic		Panic and halt the machine if an error occurs.

errors=remount-ro(*)	顼ɤ߹Ѥǥե륷ƥƥޥȤ롣
errors=continue		ե륷ƥ२顼ȯƤ³롣
errors=panic		顼ȯ顢 PANIC ơޥߤ롣

grpid			Give objects the same group ID as their creator.
bsdgroups		

grpid			֥Ȥ˺ԤƱ롼IDͿ롣
bsdgroups		

nogrpid		(*)	New objects have the group ID of their creator.
sysvgroups

nogrpid		(*)	֥ȤϺԤƱ롼IDġ
sysvgroups

resgid=n		The group ID which may use the reserved blocks.

resgid=n		ͽ֥åѤ륰롼 ID 

resuid=n		The user ID which may use the reserved blocks.

resuid=n		ͽ֥åѤ桼 ID 

sb=n			Use alternate superblock at this location.

sb=n			ΰ֤إѡ֥åȤ

quota			Quota options are currently silently ignored.
noquota			(see fs/ext3/super.c, line 594)
grpquota
usrquota

quota			Quota ץϸߡ̵ۤ뤵ޤ
noquota			(fs/ext3/super.c 594ܤ򸫤Ƥ)
grpquota
usrquota

Specification

ܺ

=============
ext3 shares all disk implementation with ext2 filesystem, and add
transactions capabilities to ext2.  Journaling is done by the
Journaling block device layer.

ext3 ϡ٤ƤΥǥ ext2 ե륷ƥȶͭ
ext2 ˥ȥ󥶥ǽɲäƤޤ
㡼ʥ󥰤ϡ㡼ʥ󥰥֥åǥХ쥤ǹԤޤ

Journaling Block Device layer

㡼ʥ󥰥֥åǥХ쥤

-----------------------------
The Journaling Block Device layer (JBD) isn't ext3 specific.  It was
design to add journaling capabilities on a block device.  The ext3
filesystem code will inform the JBD of modifications it is performing
(Call a transaction).  the journal support the transactions start and
stop, and in case of crash, the journal can replayed the transactions
to put the partition on a consistent state fastly.

㡼ʥ󥰥֥åǥХ쥤 (JBD) ϡext3 ȼΤΤǤϤޤ
֥åǥХˡ㡼ʥ󥰵ǽɲä뤿˥ǥ󤵤줿ΤǤ
ext3 ե륷ƥΥɤϡJBD ѹ¹Ԥ줿(ȥ󥶥ƤӽФ)
ȤΤޤ㡼ʥϡȥ󥶥γϡߤ򥵥ݡȤƤꡢ
å夷硢㡼ʥϥѡƥ򤹤Ф䤯̷Τʤ֤ˤ뤿ᡢ
ȥ󥶥ƽǤޤ

handles represent a single atomic update to a filesystem.  JBD can
handle external journal on a block device.

ϥɥϡե륷ƥФĤκǾñ̤ιɽޤ
JBD ϡ֥åǥХγ㡼ʥ򰷤ޤ

Data Mode

ǡ⡼
---------
There's 3 different data modes:

3Ĥΰۤʤ⡼ɤޤ:

* writeback mode
In data=writeback mode, ext3 does not journal data at all.  This mode
provides a similar level of journaling as XFS, JFS, and ReiserFS in its
default mode - metadata journaling.  A crash+recovery can cause
incorrect data to appear in files which were written shortly before the
crash.  This mode will typically provide the best ext3 performance.

* 饤ȥХå⡼
data=writeback ⡼ɤΤȤext3 Ͼ˥ǡ򥸥㡼ʥ뤷ޤ
ϡXFS, JFS, ReiserFS Υǥեȥ⡼(᥿ǡ㡼ʥ)
Ʊ٥Υ㡼ʥ󥰤󶡤ޤ
å + ꥫХ ǡåľ˽񤭹ޤ줿եǡ
뤫⤷ޤ󡣤Υ⡼ɤϡŵŪˡǹ ext3 ѥեޥ󥹤ޤ

* ordered mode
In data=ordered mode, ext3 only officially journals metadata, but it
logically groups metadata and data blocks into a single unit called a
transaction.  When it's time to write the new metadata out to disk, the
associated data blocks are written first.  In general, this mode
perform slightly slower than writeback but significantly faster than
journal mode.

* ⡼
data=ordered ⡼ɤΤȤext3 ɽ̾塢᥿ǡΤߤ򥸥㡼ʥ뤷ޤ
᥿ǡȥǡ֥åϡȥ󥶥ȸƤФ1Ĥñ̤ˡŪˤޤȤƤޤ
ǥ˿᥿ǡ񤭹顢Ϣǡ֥å
񤭹ޤޤŪˡΥ⡼ɤϡ饤ȥХå꾯٤ưȤʤޤ
㡼ʥ⡼ɤꡢʤ᤯ʤޤ

* journal mode
data=journal mode provides full data and metadata journaling.  All new
data is written to the journal first, and then to its final location. 
In the event of a crash, the journal can be replayed, bringing both
data and metadata into a consistent state.  This mode is the slowest
except when data needs to be read from and written to disk at the same
time where it outperform all others mode.

* 㡼ʥ⡼
data=journal ⡼ɤϡǡȥ᥿ǡδʥ㡼ʥ󥰤ޤ
٤Ƥοǡϡ˥㡼ʥ˽񤭹ޤ졢
θ˽ΰ֤ؽ񤭤ޤޤ
åκݡ㡼ʥϺƽ졢ǡȥ᥿ǡξ̷
̵֤˲ޤΥ⡼ɤϤäȤ٤Ǥ
ǥؤΥǡɤ߽񤭤Ʊ˹Ԥɬפϡ¾Υ⡼ɤǽǤ

Compatibility

ߴ
-------------

Ext2 partitions can be easily convert to ext3, with `tune2fs -j <dev>`.
Ext3 is fully compatible with Ext2.  Ext3 partitions can easily be
mounted as Ext2.

ext2 ѡƥϡtune2fs -j <dev>` ǡñ ext3 ѴǤޤ
ext3  ext2 ȴʸߴޤext3 ѡƥϡ
ñˡext2 ȤƥޥȤǤޤ

External Tools

ġ
==============
see manual pages to know more.

ܺ٤ϥޥ˥奢ڡ򸫤Ƥ

tune2fs: 	create a ext3 journal on a ext2 partition with the -j flags
mke2fs: 	create a ext3 partition with the -j flags
debugfs: 	ext2 and ext3 file system debugger

tune2fs: 	-j ե饰դǡext3 㡼ʥext2 ѡƥ˺ޤ
mke2fs: 	-j ե饰դǡext3 ѡƥޤ
debugfs: 	ext2 ȡext3 Υե륷ƥǥХå

References

ʸ
==========

kernel source:	file:/usr/src/linux/fs/ext3
		file:/usr/src/linux/fs/jbd

programs: 	http://e2fsprogs.sourceforge.net

useful link:
		http://www.zip.com.au/~akpm/linux/ext3/ext3-usage.html
		http://www-106.ibm.com/developerworks/linux/library/l-fs7/
		http://www-106.ibm.com/developerworks/linux/library/l-fs8/

ͥ륽:	file:/usr/src/linux/fs/ext3
		file:/usr/src/linux/fs/jbd

ץ: 	http://e2fsprogs.sourceforge.net

ʥ:
		http://www.zip.com.au/~akpm/linux/ext3/ext3-usage.html
		http://www-106.ibm.com/developerworks/linux/library/l-fs7/
		http://www-106.ibm.com/developerworks/linux/library/l-fs8/
