[tahoe-dev] [tahoe-lafs] #383: large directories take a long time to modify

[tahoe-lafs]

#383: large directories take a long time to modify
----------------------------+-----------------------------------------------
     Reporter:  warner      |        Type:  enhancement  
       Status:  new         |    Priority:  major        
    Milestone:  eventually  |   Component:  code-dirnodes
      Version:  1.0.0       |    Keywords:  dirnode      
Launchpad_bug:              |  
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Comment(by zooko):

 Tahoe-LAFS hasn't checked the HMAC since [20081221233518-92b7f-
 73eec3757419f77b23db2f52a201d0105172f5a3], 2008-12-21, which patch was
 first released in Tahoe-LAFS v1.3.0, 2009-02-13.

 If we produced dirnode entries which didn't have the HMAC tag (or which
 had a blank space instead of correct tag bytes there -- I don't know how
 the parsing works), then clients older than v1.3.0 would get some sort of
 integrity error when trying to read that entry.  Our backward-
 compatibility tradition is typically longer-duration than this.  For
 example, [source:relnotes.txt at 20090414025430-92b7f-
 6e06ebbd16f80e68a6141d44fc25cc1d49726b22 the most recent release notes]
 say that Tahoe-LAFS v1.4.1 is backwards-compatible with v1.0, and in fact
 it is actually compatible with v0.8 or so (unless you try to upload large
 files -- files with shares larger than about 4 GiB).

 So, let's not yet break compatibility by ceasing to emit the HMAC tags.

 Also, let this be a lesson to us to that if we notice forward-
 compatibility issues and fix them early then this frees us up to evolve
 the protocols earlier.  We actually stopped ''needing'' the HMAC tags when
 we released Tahoe-LAFS v0.7 in 2008-01-07, but we didn't notice that we
 were still checking them and erroring if they were wrong until the v1.3.0
 release.  So, everybody go look at
 [http://allmydata.org/trac/tahoe/search?q=forward-compatibility forward-
 compatibility issues] and fix them!

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/383#comment:3>
tahoe-lafs <http://allmydata.org>
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