[tahoe-lafs-trac-stream] [tahoe-lafs] #1496: make SFTP frontend handle updates to MDMFs without downloading and uploading the entire file

[tahoe-lafs]

#1496: make SFTP frontend handle updates to MDMFs without downloading and
uploading the entire file
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     Reporter:  zooko         |      Owner:  davidsarah
         Type:  defect        |     Status:  assigned
     Priority:  major         |  Milestone:  1.10.0
    Component:  code-mutable  |    Version:  1.8.2
   Resolution:                |   Keywords:  sftp performance mdmf
Launchpad Bug:                |
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Comment (by davidsarah):

 Replying to [comment:3 davidsarah]:
 > Replying to [comment:2 davidsarah]:
 > > Replying to [ticket:1496 zooko]:
 > > > However, I think this should probably be considered a blocker for
 1.9 final.
 > >
 > > b) for MDMF files: when the SFTP file handle is closed, overwrite only
 segments that have changed.
 >
 > As explained in ticket:393#comment:38 and ticket:393#comment:135, the
 MDMF uploader always uploads whole shares, even if its client tells it the
 regions that have changed.

 I was mistaken about that; Kevan clarified in ticket:393#comment:152 :
 > As an aside, we still do partial updates -- we just do them in such a
 > way as to ensure that all of the changes are written at once, in that we
 > retain all of the updated segments in memory as write vectors, then send
 > those all at once to the storage server.

 I still think this should not be a blocker for 1.9, though, since it's too
 big a change.

-- 
Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1496#comment:4>
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