BP-38: Bypass journal ledger

[ArvinDevel]

BP

Follow the instructions at http://bookkeeper.apache.org/community/bookkeeper_proposals/ to create a proposal.

This is the master ticket for tracking BP-38 :

To guarantee high durability, BK write journal before flush data to persistent device which will cause two write of data.
At the presence of replicating and auto-recovery mechanism, the two-write is a bit waste of the persistent device bandwidth,
especially on the scenarios which prefer weak durability guarantee.

Proposal PR - #1944

[atris]

Hi -- Unless this is being actively worked on, can I take this one?

@sijie

[sijie]

@atris yes. I don't think @ArvinDevel is actively working on this. Feel free to take this one.

[hezhangjian]

closed by #2401