[tahoe-dev] several questions about tahoe backup

David-Sarah Hopwood david-sarah at jacaranda.org
Fri Mar 2 00:03:58 UTC 2012


On 01/03/12 19:21, Brian Warner wrote:
> Repair strictly uses the k/N values from the uploaded file, *not* the
> defaults configured into the local gateway. It needs to do this because
> k and N are properties of the encoding, and are included in the filecap
> (uploading the same plaintext with different k/N values will result in
> different shares and different filecaps).
> 
> That said, I don't know how our "shares of happiness" (H) value is
> handled. I don't believe that H is stored in the share (whereas k and N
> are definitely stored in the share).

It isn't.

> I wouldn't be surprised if there's
> a bug in which repair fails because it's trying to achieve a
> locally-configured H value on a file that was encoded with very
> different k/N values (say k=1 N=2 but H=5).

That *should* fail, in the sense of reporting that the file has not been
successfully repaired to the configured happiness threshold. But it should
attempt to ensure that N shares have been stored on distinct servers first.
I don't know whether it does that correctly.

-- 
David-Sarah Hopwood ⚥

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