ext3cow - A file system that preserves the past
The ext3cow file system has been released for the 2.6 Linux kernel. This extension to ext3 adds "copy on write" (cow) functionality, which in turn allows the user to view the file system as it existed in the past. Unlike fixed checkpointing, this means that a user could dial in any time whatsoever, and see a consistent filesystem from that moment. It would be interesting to see what the performance characteristics of the system are.
If you're interested, you can get it from ext3cow.com
; it consists of a kernel patch based on kernel 188.8.131.52, as well as some userland tools.
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