HBASE-6466 add the possibility to have multiple threads for the flusher.
The default value is 1, but this should be incremented to 2 reasons:
- I've observed that the flush of a region can be delayed because another is in progress. During a write load, this leads to an increased latency because the memstore size increases and then block the client
- if, by accident, a flusher hits a slow or bad datanode, all the flush will have to wait until the timeouts expires. With 2 or more flushers and some luck the other regions will be flushed by the second thread.
Lastly this setting is important enough to be documented in the standard hbase site imho.
I think it's important enough to go in the .98 branch as well
There will be an impact: as the flush won't be queued (or less queued) we may have more compactions...