Commentaires cluster change + slide 19

slides.md

@@ -395,6 +395,16 @@ AppendEntries RPCs include <index, term> of entry preceding new one(s)
 
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+- Dashed lines show configuration entries that have been created but not committed, 
+- solid lines show the latest committed configuration entry. 
+- The leader first creates the Cold,new configuration entry in its log and commits it to Cold,new (a majority of Cold and a majority of Cnew). 
+- Then it creates the Cnew entry and commits it to a majority of Cnew. 
+- There is no point in time in which Cold and Cnew can both make decisions independently.
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@@ -427,6 +437,14 @@ AppendEntries RPCs include <index, term> of entry preceding new one(s)
 
 ![bg 90%](https://ongardie.net/static/coreosfest/slides/timeoutcdf.svg)
 
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+- a small amount of randomization in the election timeout is enough to avoid split votes in elections. 
+- In the absence of randomness, leader election consistently took longer than 10 seconds in our tests due to many split votes. Adding just 5ms of randomness helps significantly, resulting in a median downtime of 287ms. 
+- Using more randomness improves worst-case behavior: with 50ms of randomness the worstcase completion time (over 1000 trials) was 513ms.
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