[tahoe-dev] Tahoe performance

Shawn Willden shawn-tahoe at willden.org
Thu Feb 19 02:12:26 UTC 2009

On Wednesday 18 February 2009 06:34:16 pm Brian Warner wrote:
> When rsync is used locally (i.e. no ssh), I don't know whether it uses this
> algorithm, or if it just compares timestamps and does a one-read/one-write
> copy when the timestamps don't match. 

The man page says it goes into whole-file mode when both paths are local.

> The tool that Shawn is building sounds like it's designed to accomplish all
> of these goals, and then some, at the expense of having the resulting
> filesystem be mostly stored in a custom database (i.e. regular Tahoe nodes
> won't know how to interpret it, so you couldn't view one of the directories
> without that tool, and you couldn't share just a piece of the filesystem
> with someone else).

Hmm.  It wouldn't be that difficult to add a new sort of dirnode which is an 
revlog-ish index referencing all of the revisions (some full, some deltas) 
for a particular file.  With that in place, including a URI syntax for 
referencing a particular revision, and core Tahoe support for extracting the 
requested revision, it would be easy to create a navigable dirnode tree.

I started down that path (the revlog-ish index) at one point, and then veered 
off a different direction.  Now I'm not sure why I did :-)  I need to go back 
and look at my notes to see if the decision was for some compelling reason.  
If not, it may be worth veering back.


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