| ext3 | | Developer | Stephen Tweedie | | Full name | Third extended file system | | Introduced | November 2001 (Linux 2.4.15) | | Partition identifier | 0x83 (MBR)
EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 (GPT) | | Structures | | Directory contents | Table, H tree with dir_index enabled | | File allocation | bitmap (free space), table (metadata) | | Bad blocks | Table | | Limits | | Max file size | 16 GiB – 2 TiB | | Max number of files | Variable[1] | | Max filename length | 255 bytes | | Max volume size | 2 TiB – 16 TiB | | Allowed characters in filenames | All bytes except NUL and '/' | | Features | | Dates recorded | modification (mtime), attribute modification (ctime), access (atime) | | Date range | December 14, 1901 - January 18, 2038 | | Date resolution | 1s Nanosecond (using undocumented big i-node) For other uses, see Software developer (disambiguation). ...
Dr Stephen C. Tweedie is a software developer who is known for his work on the Linux kernel, in particular the ext3 filesystem. ...
November 2001 : January - February - March - April - May - June - July - August - September - October - November - December November - The Doha Declaration slightly relaxes the grip of international intellectual property. ...
This article is about operating systems that use the Linux kernel. ...
In computer engineering, hard disk drive partitioning is the creation of logical divisions upon a hard disk that allows one to apply operating system-specific logical formatting. ...
A Master Boot Record (MBR), or partition sector, is the 512-byte boot sector that is the first sector (Sector 0) of a partitioned data storage device such as a hard disk. ...
This article or section may be confusing or unclear for some readers, and should be edited to rectify this. ...
GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical hard disk. ...
The first ten levels of an H tree The H tree (so called because its first two steps resemble the letter H) is a family of fractal sets whose Hausdorff dimension is equal to 2. ...
A gibibyte is a unit of information or computer storage. ...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
is the 348th day of the year (349th in leap years) in the Gregorian calendar. ...
Year 1901 (MCMI) was a common year starting on Tuesday (link will display calendar) of the Gregorian calendar (or a common year starting on Monday [1] of the 13-day-slower Julian calendar). ...
is the 18th day of the year in the Gregorian calendar. ...
2038 (MMXXXVIII) will be a common year starting on Friday of the Gregorian calendar. ...
| | Forks | | | Attributes | No-atime, append-only, synchronous-write, no-dump, h-tree (directory), immutable, journal, secure-delete, top (directory), allow-undelete | | File system permissions | Unix permissions, ACLs and arbitrary security attributes (Linux 2.6 and later) | | Transparent compression | No | | Transparent encryption | No (provided at the block device level) | | Supported operating systems | Linux, BSD, Windows (through an IFS) | The ext3 or third extended filesystem is a journaled file system that is commonly used by the Linux operating system. It is the default file system for many popular Linux distributions. Stephen Tweedie first revealed that he was working on extending ext2 in a February 1999 kernel mailing list posting[2] and the filesystem was merged with the mainline Linux kernel in November 2001 from 2.4.15 onward.[3] In computer file systems, a fork is additional data associated with a file system object. ...
Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ...
In computer security, an access control list (ACL) is a list of permissions attached to an object. ...
Filesystem-level encryption, is a form of disk encryption where individual files or directories are encrypted by the file system, in contrast to full disk encryption where the entire partition or disk, where the file system resides, is encrypted. ...
An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ...
The Installable File System (IFS) is a Filesystem API in IBM OS/2 and Microsoft Windows NT that enables the operating system to recognize and load drivers for filesystems. ...
A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ...
This article is about operating systems that use the Linux kernel. ...
An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ...
For library and office filing systems, see Library classification. ...
A Linux distribution or GNU/Linux distribution (or a distro) is a Unix-like operating system plus application software comprising the Linux kernel, the GNU operating system, assorted free software and sometimes proprietary software, all created by individuals, groups or organizations from around the world. ...
Dr Stephen C. Tweedie is a software developer who is known for his work on the Linux kernel, in particular the ext3 filesystem. ...
The ext2 or second extended file system is a file system for the Linux kernel. ...
The Linux kernel is a Unix-like operating system kernel. ...
Advantages
Although its performance (speed) is less attractive than competing linux filesystems such as JFS, ReiserFS and XFS, it does have the significant advantage that it allows in-place upgrades from the ext2 file system without having to back up and restore data as well as requiring lower CPU consumption than ReiserFS and XFS.[4]-1...
ReiserFS is a general-purpose, journaled computer file system designed and implemented by a team at Namesys led by Hans Reiser who is referred to as the projects Benevolent Dictator for Life. ...
XFS is a high-performance journaling file system created by Silicon Graphics for their IRIX operating system. ...
For other uses of Backup, see Backup (disambiguation). ...
The ext3 file system adds, over its predecessor:
Without these, any ext3 file system is also a valid ext2 file system. This has allowed well-tested and mature file system maintenance utilities for maintaining and repairing ext2 file systems to also be used with ext3 without major changes. The ext2 and ext3 file systems share the same standard set of utilities, e2fsprogs, which includes a fsck tool. The close relationship also makes conversion between the two file systems (both forward to ext3 and backward to ext2) straightforward. A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ...
B-trees are tree data structures that are most commonly found in databases and filesystem implementations. ...
e2fsprogs (sometimes called the e2fs programs) is a set of utilities for maintaining the ext2 and ext3 file systems. ...
The system utility fsck (for file system check or file system consistency check) is a tool for checking the consistency of a file system in the Unix system and clones thereof. ...
There are three levels of journaling available in the Linux implementation of ext3:
- Journal (lowest risk)
- Both metadata and file contents are written to the journal before being committed to the main file system. Because the journal is relatively continuous on disk, this can improve performance in some circumstances. In other cases, performance gets worse because the data must be written twice - once to the journal, and once to the main part of the filesystem.
- Ordered (medium risk)
- Only metadata is journaled; file contents are not, but it's guaranteed that file contents are written to disk before associated metadata is marked as committed in the journal. This is the default on many Linux distributions. If there is a power outage or kernel panic while a file is being written or appended to, the journal will indicate the new file or appended data has not been "committed", so it will be purged by the cleanup process. (Thus appends and new files have the same level of integrity protection as the "journaled" level.) However, files being overwritten can be corrupted because the original version of the file is not stored. Thus it's possible to end up with a file in an intermediate state between new and old, without enough information to restore either one or the other (the new data never made it to disk completely, and the old data is not stored anywhere). Even worse, the intermediate state might intersperse old and new data, because the order of the write is left up to the disk's hardware.[5] [6]
- Writeback (highest risk)
- Only metadata is journaled; file contents are not. The contents might be written before or after the journal is updated. As a result, files modified right before a crash can become corrupted. For example, a file being appended to may be marked in the journal as being larger than it actually is, causing garbage at the end. Older versions of files could also appear unexpected after a journal recovery. The lack of syncronicity between data and journal is faster in many cases. XFS and JFS use this level of journaling, but ensure that any "garbage" due to unwritten data is zeroed out on reboot.
While in some contexts the lack of "modern" filesystem features such as dynamic inode allocation and extents could be considered a disadvantage, in terms of recoverability this gives ext3 a significant advantage over file systems with those features. The file system metadata is all in fixed, well-known locations, and there is some redundancy inherent in the data structures that may allow ext2 and ext3 to be recoverable in the face of significant data corruption, where tree-based file systems may not be recoverable. Linux kernel panic under QEMU. Mac OS X kernel panic alert. ...
Disadvantages
Functionality Since ext3 aims at being mostly compatible with ext2, many of the on-disk structures are similar to those of ext2. Because of that, ext3 lacks a number of features of more recent designs, such as dynamic allocation of i-nodes and variable block sizes (frags or tails).
ext3 filesystems cannot be fscked while the filesystem is mounted for writing. A dump of the filesystem taken while it is mounted read-write may result in corrupt data within the dump file. The system utility fsck (for file system check or file system consistency check) is a tool for checking the consistency of a file system in the Unix system and clones thereof. ...
ext3 does not support extents, a feature found in other filesystems such as JFS, ext4 and XFS. An extent is a contiguous area of storage in a computer file system, reserved for a file. ...
-1...
The ext4, or fourth extended filesystem is a journalled file system that was revealed on October 10, 2006 by Andrew Morton as a compatible improvement to the ext3, featuring support for volumes up to 1024 petabytes and added extent (allocation of an area for a file to use) support. ...
XFS is a high-performance journaling file system created by Silicon Graphics for their IRIX operating system. ...
Ext3 has a sub-directory limit of 32768
Defragmentation There is no online ext3 defragmentation tool working on the filesystem level. An offline ext2 defragmenter, e2defrag, exists but requires that the ext3 filesystem be converted back to ext2 first. But depending on the feature bits turned on the filesystem, e2defrag may destroy data; it does not know how to treat many of the newer ext3 features.[7] In the context of administering computer systems, defragmentation is a process that reduces the amount of fragmentation in file systems. ...
There are userspace defragmentation tools like Shake[8] and defrag [9]. Shake works by allocating space for the whole file bolt upright and hoping that it will make the newly allocated file less fragmented. It also tries to write files used at the same time next to each other. Defrag works by copying each file over itself.
However they only work if the filesystem is reasonably empty. A true defragmentation tool does not exist for ext3.[10]
That being said, as the Linux System Administrator Guide states, "Modern Linux filesystem(s) keep fragmentation at a minimum by keeping all blocks in a file close together, even if they can't be stored in consecutive sectors. Some filesystems, like ext3, effectively allocate the free block that is nearest to other blocks in a file. Therefore it is not necessary to worry about fragmentation in a Linux system."[11]
Irrespective of the above (subjective) statement, file fragmentation can be an important issue in server environments such as in multi-media server applications. While it is true that ext3 is more resistant to file fragmentation than FAT filesystems, nonetheless ext3 filesystems can and do get fragmented over time. Consequently the successor to the ext3 filesystem, ext4, includes a filesystem defragmentation utility and support for extents (contiguous file regions). The ext4, or fourth extended filesystem is a journalled file system that was revealed on October 10, 2006 by Andrew Morton as a compatible improvement to the ext3, featuring support for volumes up to 1024 petabytes and added extent (allocation of an area for a file to use) support. ...
Further examples in which lack of defragmentation in some Linux filesystems (such as ext3) is a serious issue, includes server applications where rapid, concurrent and random file creation, update or access occurs. Such systems include large-scale carrier grade voice mail systems, Media-Messaging Service Centers (MMSCs) and SMS/SMSCs (Short Message Service Centers) servers. Media servers such as large scale voice mail and UMS servers are required to stream hundreds of voice or video streams concurrently to hundreds of users in near real-time conditions. These types of applications are particularly susceptible to file fragmentation; access delays during playback of a voice (e.g. voice mail) or video file, due to multiple fragmentation in the media file, can lead to playback interruption or distortion. As fragmentation increases over time, service capacity of these systems degrades because of increased CPU and I/O overhead resulting from fragmentation induced disk thrashing.
Compression Support for transparent compression is available as an unofficial patch for ext3. This patch is a direct port of e2compr and still needs further development, it compiles and boots well with upstream kernels but journaling is not implemented yet. The current patch is named e3compr and can be found here: http://sourceforge.net/projects/e3compr/ Source coding redirects here. ...
Size limits ext3 has a maximum size for both individual files and the entire filesystem. For the filesystem as a whole that limit is 2**31-1 blocks. Both limits are dependent on the block size of the filesystem; the following chart summarizes the limits[12]: It should be noted that the 8 KiB block size is only available on architectures which allow 8 KiB pages (such as Alpha). A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
A gibibyte is a unit of information or computer storage. ...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
A gibibyte is a unit of information or computer storage. ...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes...
A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...
This article is about computer virtual memory. ...
DEC Alpha AXP 21064 Microprocessor die photo Package for DEC Alpha AXP 21064 Microprocessor Alpha AXP 21064 bare die mounted on a business card with some statistics The DEC Alpha, also known as the Alpha AXP, is a 64-bit RISC microprocessor originally developed and fabricated by Digital Equipment Corp...
No checksumming in journal | | This article or section needs to be updated.
Please update the article to reflect recent events / newly available information, and remove this template when finished. | Ext3 does not do checksumming when writing to the journal. If barrier=1 is not enabled as a mount option (in /etc/fstab), and if the hardware is doing out-of-order write caching, one runs the risk of severe filesystem corruption during a crash.[13][14] (This option is not enabled by default on almost all popular Linux distributions, and thus most distributions are at risk.) A checksum is a form of redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space (telecommunications) or time (storage). ...
Consider the following scenario: If hard disk writes are done out-of-order (due to modern hard disks caching writes in order to amortize write speeds), it is likely that one will write a commit block of a transaction before the other relevant blocks are written. If a power failure or unrecoverable crash should occur before the other blocks get written, the system will have to be rebooted. Upon reboot, the file system will replay the log as normal, and replay the "winners" (transactions with a commit block, including the invalid transaction above which happened to be tagged with a valid commit block). The unfinished disk write above will thus proceed, but using corrupt journal data. The file system will thus mistakenly overwrite normal data with corrupt data while replaying the journal. If checksums had been used (if the blocks of the "fake winner" transaction were tagged with a mutual checksum), the file system could have known better and not replayed the corrupt data onto the disk. This is fixed in EXT4 In computational complexity theory, amortized analysis is the time per operation averaged over a worst_case sequence of operations. ...
Ext4dev / Ext4 -
An enhanced version of the filesystem is under development; it was announced by Theodore Ts'o [15] on June 28, 2006 under the name of ext4. The ext4, or fourth extended filesystem is a journalled file system that was revealed on October 10, 2006 by Andrew Morton as a compatible improvement to the ext3, featuring support for volumes up to 1024 petabytes and added extent (allocation of an area for a file to use) support. ...
Theodore Ted Tso is a software developer known for his contributions to the Linux kernel, in particular his contributions to filesystems. ...
is the 179th day of the year (180th in leap years) in the Gregorian calendar. ...
Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...
References
See also The ext2 or second extended file system is a file system for the Linux kernel. ...
The following lists identify, characterise and link to more thorough information on computer file systems. ...
The following tables compare general and technical information for a number of file systems. ...
Extended file attributes is a file system feature that enables users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or records of creation and modification times). ...
External links - Linux ext3 FAQ as of 2004-10-14.
- Introducing ext3 - IBM developerWorks Advanced filesystem implementor's guide, Part 7
- Ext2 File System For Windows GPL ext2/ext3 file system driver for Windows NT/2000/XP/Vista (opensource, supports read & write)
- Ext2 Installable File System For Windows ext2/ext3 file system driver for MS Windows NT/2000/XP (freeware, supports read & write on Windows NT4.0/2000/XP/2003/Vista on x86/AMD64)
- EXT2 IFS ext2/ext3 file system driver for MS Windows NT/2000/XP (opensource, doesn't support writing, doesn't support Windows XP SP2 or Windows Vista)
- Explore2fs An explorer-like GUI tool for accessing ext2/ext3 filesystems under MS Windows
- ext2/ext3 resizing tools
- Presentation on EXT3 Journaling Filesystem by Dr. Stephen Tweedie at the Ottawa Linux Symposium, 20 July 2000
- Tutorial - Determining Your EXT3 Size Limits
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