need feedback on durability performance

Hey Michael,

Can you take a look at the performance matrix I compiled for durability. Here is the sheet: https://docs.google.com/spreadsheets/d/1B8v4OZneOeGxJwUj226zA3YDr0Y0gjRSVLwy0IAP9qw/edit?usp=sharing . SDK2 and SDK3 columns are for old durability params (replicate to and persist to) and SDK3 New is the new durability levels. There are two issues that I am confused by and need some input to make sure I did the testing correctly. First: For SDK3 New, all durability levels except durabilityLevel=None have the same performance. To me, it does not make sense why majority and persistMajority would perform the same. Also, the performance impact is severe, dropping from 387k to 1k going from None to majority, >99% drop. Second: SDK3 with replicateTo=1 persistTo=0 performs significantly slower than replicateTo=1 persistTo=1 and replicateTo=1 persistTo=2, which implies that adding persist to increases performance and this doesn't really make sense. 

Here is my YCSB code I am using for the tests, I create a branch called couchbase3-new-durability based on couchbase3 branch: https://github.com/couchbaselabs/YCSB/blob/couchbase3-new-durability/couchbase3/src/main/java/com/yahoo/ycsb/db/couchbase3/Couchbase3Client.java

Here is the set of test files I am using: https://github.com/couchbase/perfrunner/tree/master/tests/durability