Questions about Drill's multi-thread model

[weijie tong]

Hi there，
   Our product environment has a situation that if one query was blocked by
the storage,then all other queries which come later would took long and
long time to run even they really just need fewer time. At the time ,the
cluster's load is not too high.
    I know that every foreman will run in dedicated different  threads. I
want to know that IO threads model,whether they are shared by different
foremans' threads. How to explain last scenario's behavior?