Hi,
Christopher Li wrote:
> On Sat, Apr 09, 2005 at 04:31:10PM -0700, Linus Torvalds wrote:
> > NOTE! This means that each "tree" file basically tracks just a
> > single directory. The old style of "every file in one tree file"
> > still works, but fsck-cache will warn about it. Happily, the git
> > archive itself doesn't have any subdirectories, so git itself is not
> > impacted by it.
>
> That is really cool stuff. My way to read it, correct me if I am
> wrong, git is a user space version file system. "tree" <--> directory
> and "blob" <--> file. "commit" to describe the version history.
See the Venti filesystem in Bell Labs's Plan 9 OS. It too uses SHA-1.
http://www.cs.bell-labs.com/sys/doc/venti/venti.pdf
Abstract
This paper describes a network storage system, called Venti,
intended for archival data. In this system, a unique hash of a
block's contents acts as the block identifier for read and write
operations. This approach enforces a write-once policy, preventing
accidental or malicious destruction of data. In addition, duplicate
copies of a block can be coalesced, reducing the consumption of
storage and simplifying the implementation of clients. Venti is a
building block for constructing a variety of storage applications
such as logical backup, physical backup, and snapshot file systems.
We have built a prototype of the system and present some preliminary
performance results. The system uses magnetic disks as the storage
technology, resulting in an access time for archival data that is
comparable to non-archival data. The feasibility of the write-once
model for storage is demonstrated using data from over a decade's
use of two Plan 9 file systems.
Cheers,
Ralph.
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