In the updated MOB design however, admins can set CF level thresholds that would force cell values > the threshold to use the MOB write path instead of the traditional path. There are two cases where mobs need to interact with this threshold
1) How do we handle the case when the threshold size is changed?
2) Today, you can bulkload hfiles that contain MOBs. These cells will work as normal inside hbase. Unfortunately the cells with MOBs in them will never benefit form the MOB write path.
The proposal here is to modify compaction in mob enabled cf's such that the threshold value is honored with compactions. This handles case #1 – elements that should be moved out of the normal hfiles get 'compacted' into refs and mob hfiles, and values that should be pulled into the cf get derefed and written out wholy in the compaction. For case #2, we can maintain the same behavior and compaction would move data into the mob writepath/lifecycle.