title: How to make FIO replay a trace with multiple thread
body: <p>I'm trying to use fio to replay some block traces.</p>
  
  <p>The job file I wrote looks like: </p>
  
  <pre><code>[global]
  name=replay
  filename=/dev/md0
  direct=1 
  ioengine=psync
  
  [replay]
  read_iolog=iolog.fio
  replay_no_stall=0 
  write_lat_log=replay_metrics
  numjobs=1
  </code></pre>
  
  <p>The key here is I want to use "psync" as the ioengine, and replay the iolog.
  However, with psync, fio seems to ignore "replay_no_stall" option, which ignore the timestamp in the iolog.</p>
  
  <p>And by setting numjobs to be 4, fio seems to make 4 copies of the same workload, instead of using 4 threads to split the workload.</p>
  
  <p>So, how could I make fio with psync respect the timestamp, and use multiple threads to replay the trace?</p>