[volunteergrid2-l] Phase 2

[David-Sarah Hopwood]

On 05/04/12 18:48, Shawn Willden wrote:
> On Thu, Apr 5, 2012 at 11:41 AM, Ted Rolle, Jr. <stercor at gmail.com
> <mailto:stercor at gmail.com>> wrote:
>     On 04/05/2012 01:31 PM, erpo41 at gmail.com <mailto:erpo41 at gmail.com> wrote:
>>
>>     Unless I misread the pdf on the tahoe-lafs site, N is limited to 256...
>>
>     This is one of those things that, like the law, can be changed by pen or keystroke.
> 
> Unless there's some single-byte field in the protocol that holds a "short node ID", [...]

Not for the node id or sharenum, but k and N are stored as single-byte fields
in the mutable share container format:

https://tahoe-lafs.org/trac/tahoe-lafs/browser/git/src/allmydata/mutable/layout.py?rev=87ca4fc7#L27

It would be easy to change this format, but this isn't by itself a compelling
enough reason to do so, IMHO. If the format were changed, old clients would
not be able to read shares in the new format, but we wouldn't expect them to
be able to anyway, because the erasure coding algorithm would also need to be
changed for both mutable and immutable shares (the current one is based on
GF(2^256) arithmetic). So if we made this change, we'd probably only do it at
the same time as some other major upgrade that broke backward compatibility
for new shares.

-- 
David-Sarah Hopwood ⚥

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