anchor.diff:  the whole data centre loses power at the same time, then it is possible that
   you could lose the last 5 seconds (or `sync_interval`) of data.
   
  -******************************************************
  +We are constantly monitoring the perfromance implications of better default
  +translog sync semantics, so the default might change as time passes and HW,
  +virtualization, and other aspects improve.
  +
  +******************************************************
positive.code: to the `sync_interval`.
  
  The `buffered` translog is written to disk when it reaches 64kB in size, or
  whenever an `fsync` is triggered by the `sync_interval`.
  
  .Why don't we `fsync` the translog after every write?
  ******************************************************
  
negative.code: However, the translog is not the only persistence mechanism in Elasticsearch.
  Any index or update request is first written to the primary shard, then
  forwarded in parallel to any replica shards. The primary waits for the action
  to be completed on the replicas before returning success to the client.
  
  If the node holding the primary shard dies for some reason, its transaction
  log could be missing the last 5 seconds of data. However, that data should
  