[tahoe-dev] Tahoe performance

Shawn Willden shawn-tahoe at willden.org
Thu Feb 19 19:48:20 UTC 2009

On Wednesday 18 February 2009 08:44:51 pm Brian Warner wrote:
> True, but the reason our MDMF plans are different (storing the full/deltas
> in the file object, rather than the directory) is to allow someone to share
> a single mutable file, without sharing the directory that contains it.

Mmm, that's not an issue with what I was suggesting.  What I was thinking of 
was a sort of a dirnode variant that would only contain revisions of a single 
file.  In some sense it "is" the file; it just doesn't actually contain any 
of the content except by reference.

> Also, one design for a versioned file (mutable or immutable) would be to
> have a "master file" which contains a list of immutable filecaps, some of
> which point to full versions, others which point to deltas, and the master
> would have instructions on how to reassemble the pieces

Yes, this is what I was referring to.

> (the simplest form 
> wouldn't even use deltas, just full versions). But we don't plan to do it
> that way. The reason we're thinking of revlog-ish for LDMF instead is the
> segmentation problem: the reliability/availability drops sharply when the
> overall file is composed of many separate immutable files.

This is true.  I plan to force full versions periodically, in order to limit 
the risk of a large number of versions becoming unavailable due to the loss 
of one immutable file.


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