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

tahoe-lafs trac at allmydata.org
Sat Aug 15 02:52:45 UTC 2009


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

Comment(by zooko):

 Hm, good points, Kevan.

 So, for the case of off-site backup where you don't care how many servers
 need to stay up in order to guarantee the availability of your data, then
 you should set {{{servers_of_happiness=1}}}, right?

 And for the case that you have {{{K=3}}} and {{{M=10}}}, then we ''could''
 extend the upload peer selection algorithm so that if you have
 {{{servers_of_happiness=2}}} then it has to put more than one share on
 each server, and in such a way that there are no two servers which have
 the same two shares.  But instead we could make it so that your upload
 fails with the error "Didn't upload it in such a way that the survival of
 any 2 servers was sufficient for the survival of the file.", then you
 realize that if that's what you want you ought to set {{{K=2}}} and re-
 upload.

 How does that sound?

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/778#comment:7>
tahoe-lafs <http://allmydata.org>
secure decentralized file storage grid


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