ext3cow
| Developer(s) | 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 |
|---|---|
| Full name | Third extended file system with copy-on-write |
| Introduced | July 2003 with Linux |
| 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 |
| Max no. 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 | Yes (provided at the block device level) |
| Other | |
| Supported operating systems | Linux, BSD, Windows (through an IFS) |
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, giving ext3cow the "cow" in its name. Details on ext3cow's implementation can be found in Ext3cow: A Time-Shifting File System for Regulatory Compliance [1].
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.
It shares many of its performance characteristics with ext3.
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 2.6 kernel was released on March 30, 2007.
References
- ^ Zachary Peterson and Randal Burns (May, 2005). "Ext3cow: A Time-Shifting File System for Regulatory Compliance" (PDF). ACM Transactions on Storage, 1(2).
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