[tahoe-lafs-trac-stream] [tahoe-lafs] #549: MODE_WRITE mapupdate: maybe increase epsilon to handle large batches of new servers better

[tahoe-lafs]

#549: MODE_WRITE mapupdate: maybe increase epsilon to handle large batches of new
servers better
-------------------------+-------------------------------------------------
     Reporter:  warner   |      Owner:  bazuka
         Type:  defect   |     Status:  new
     Priority:  major    |  Milestone:  soon
    Component:  code-    |    Version:  1.2.0
  mutable                |   Keywords:  availability upload easy mutable
   Resolution:           |  ucwe
Launchpad Bug:           |
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Changes (by bazuka):

 * owner:   => bazuka


Old description:

> Part of the problem described in #546 is due to adding a large number of
> new servers. This inserts large gaps in the permuted server list, and the
> mapupdate code that handles MODE_WRITE may not look far enough to get
> past the gaps.
>
> It might be a good idea to increase the "epsilon" used for MODE_WRITE
> from its current value of "k" (usually 3) to "N" (usually 10). As noted
> at the bottom of #546, if all the servers are writeable, this should be
> enough to make sure we don't need to send any shares to unqueried
> servers.

New description:

 Part of the problem described in #546 is due to adding a large number of
 new servers. This inserts large gaps in the permuted server list, and the
 mapupdate code that handles MODE_WRITE may not look far enough to get past
 the gaps.

 It might be a good idea to increase the "epsilon" used for MODE_WRITE from
 its current value of "k" (usually 3) to "N" (usually 10). As noted at the
 bottom of #546, if all the servers are writeable, this should be enough to
 make sure we don't need to send any shares to unqueried servers.

--

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/549#comment:5>
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