[tahoe-dev] [tahoe-lafs] #778: "shares of happiness" is the wrong measure; "servers of happiness" is better
tahoe-lafs
trac at allmydata.org
Tue Aug 18 12:20:29 PDT 2009
#778: "shares of happiness" is the wrong measure; "servers of happiness" is
better
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Reporter: zooko | Owner:
Type: defect | Status: new
Priority: critical | Milestone: undecided
Component: code-peerselection | Version: 1.4.1
Keywords: reliability | Launchpad_bug:
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Comment(by davidsarah):
> If {{{k_e / k}}} is not an integer, the minimal {{{m_e}}} is a little
more complicated. In that case, most of the servers must have {{{1 + k_e
// k}}} shares, but {{{k-1}}} of them only need {{{k_e // k shares}}}.
> So {{{m_e = (n-k-1)*(1 + k_e // k) + (k-1)*(1 + k_e // k)}}}.
Rearranging gives {{{m_e = n - k + 1 + n * (k_e // k)}}}.
The first expression for {{{m_e}}} is wrong, even though the rest of the
argument and the rearranged version is correct. What you mean is:
... So {{{m_e = (n-(k-1))*(1 + k_e // k) + (k-1)*(k_e // k)}}}.
Rearranging gives {{{m_e = n - k + 1 + n * (k_e // k)}}}.
--
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/778#comment:27>
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