Summary: Since we are optimizing for server workloads, some default values are not optimized any more. We change some of those values that I feel it's less prone to regression bugs.
Test Plan: make all check
Reviewers: dhruba, haobo, ljin, igor, yhchiang
Reviewed By: igor
CC: leveldb, MarkCallaghan
Differential Revision: https://reviews.facebook.net/D16995