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| Developer(s) | Zachary Peterson (ext3cow versioning),Stephen Tweedie (ext3 design and implementation),Rémy Card (originalext2 design and implementation),Theodore Ts'o (tools and improvements),Andreas Gruenbacher (xattrs and ACLs),Andreas Dilger (online resizing), et al. |
|---|---|
| Full name | Third extended file system with copy-on-write |
| Introduced | July 2003; 22 years ago (2003-07) withLinux |
| Partition IDs | 0x83 (MBR) EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 (GPT) |
| Structures | |
| Directory contents | Table, Tree |
| File allocation | bitmap (free space), table (metadata) |
| Bad blocks | Table |
| Limits | |
| Max volume size | 8TiB |
| Max file size | 2TiB |
| Maxno. of files | Variable1 |
| Max filename length | 255 bytes |
| Allowed filename characters | 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 |
| Forks | 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) |
| Transparent compression | No |
| Transparent encryption | No (provided at the block device level) |
| Other | |
| Supported operating systems | Linux |
Ext3cow orthird extended filesystem with copy-on-write is anopen source,versioning file system based on theext3 file system. Versioning is implemented through block-levelcopy-on-write. It shares many of its performance characteristics withext3.
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 US electronic record retention legislation, such asSarbanes–Oxley andHIPAA.
A version of ext3cow for theLinux 2.6 kernel was released on March 30, 2007.
Details on ext3cow's implementation can be found in a 2005 paper.[1]
