[tahoe-dev] [tahoe-lafs] #778: "shares of happiness" is the wrong measure; "servers of happiness" is better

[tahoe-lafs]

#778: "shares of happiness" is the wrong measure; "servers of happiness" is
better
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 Reporter:  zooko               |           Owner:  kevan    
     Type:  defect              |          Status:  new      
 Priority:  critical            |       Milestone:  undecided
Component:  code-peerselection  |         Version:  1.4.1    
 Keywords:  reliability         |   Launchpad_bug:           
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Changes (by zooko):

  * owner:  => kevan


Comment:

 Kevan: go for it!

 Everyone: please move discussion of improving FEC parameters and/or server
 selection to #791 (Optimize FEC parameters), and leave this ticket to
 track Kevan's progress on documenting, testing, and implementing the
 simpler goal.  That goal is:
  * Use the user-configured FEC parameters {{{k}}}, {{{n}}}, and {{{h}}}
 ("happiness"), just as Tahoe-LAFS v1.5 does.
  * Use the current server-selection algorithm which is already implemented
 in Tahoe-LAFS v1.5.
  * After the server-selection has chosen the initial set of servers to
 use, test whether that selection would satisfy the criterion of
 "Reliability level is at least {{{k}}}-out-of-{{{h}}} servers.".  If it
 wouldn't, abort the upload.
  * Whenever a server fails to accept shares which the client had intended
 to upload to that server, such as by disconnecting during an upload or
 returning an error message instead of storing a block, then recalculate
 whether the new set of servers would satisfy the criterion.  If not, abort
 the upload.

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/778#comment:36>
tahoe-lafs <http://allmydata.org>
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