Ext3cow

infobox filesystem
name = ext3cow
full_name = Third extended file system with copy-on-write
developer = Zachary Peterson (ext3cow versioning), Stephen Tweedie (ext3 design and implementation), Rémy Card (original ext2 design and implementation), Theodore Ts'o (tools and improvements), Andreas Gruenbacher (xattrs and ACLs), Andreas Dilger (online resizing), et al
introduction_os = Linux
introduction_date = July 2003
partition_id = 0x83 (MBR)
EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 (GPT)
directory_struct = Table, Tree
file_struct = bitmap (free space), table (metadata)
bad_blocks_struct = Table
max_filename_size = 255 bytes
max_files_no = Variable¹
max_volume_size = 8TiB
max_file_size = 2TiB
filename_character_set = All bytes except NUL and '/'
dates_recorded = modification (mtime), attribute modification (ctime), access (atime)
date_range = December 14, 1901 - January 18, 2038
date_resolution = 1s
forks_streams = Yes
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)
compression = No
versioning = Yes
encryption = No (provided at the block device level)
OS = Linux

Ext3cow or third extended filesystem with copy-on-write is an open source, versioning file system based on the ext3 file system. Versioning is implemented through block-level copy-on-write. It shares many of its performance characteristics with ext3.

Ext3cow provides a time-shifting interface that permits a real-time and continuous view of data in the past. Time-shifting is a novel interface, introduced in ext3cow, allowing users to navigate through and access past namespaces by adding a time component to their commands.

Ext3cow was designed to be a platform for compliance with the versioning and auditability requirements of recent electronic record retention legislation, such as Sarbanes-Oxley and HIPAA.

A version of ext3cow for the Linux 2.6 kernel was released on March 30, 2007.

Details on ext3cow's implementation can be found in a 2005 paper. [cite web | url=http://hssl.cs.jhu.edu/papers/peterson-tos05.pdf | title=Ext3cow: A Time-Shifting File System for Regulatory Compliance | author=Zachary Peterson and Randal Burns| month=May | year=2005 | work=ACM Transactions on Storage, 1(2)|format=PDF]

References

See also

* ext3
* List of file systems
* Comparison of file systems

External links

* [http://www.ext3cow.com/ ext3cow homepage]
* [http://freshmeat.net/projects/ext3cow/ ext3cow Freshmeat entry]