[rbranson]

You're right. Sync writes are ten times as slow. 331µs.

  write: IOPS=3007, BW=11.7MiB/s (12.3MB/s)(118MiB/10001msec); 0 zone resets
    clat (usec): min=196, max=23274, avg=331.13, stdev=220.25
     lat (usec): min=196, max=23275, avg=331.25, stdev=220.27
    clat percentiles (usec):
     |  1.00th=[  210],  5.00th=[  223], 10.00th=[  235], 20.00th=[  262],
     | 30.00th=[  297], 40.00th=[  318], 50.00th=[  330], 60.00th=[  343],
     | 70.00th=[  355], 80.00th=[  371], 90.00th=[  400], 95.00th=[  429],
     | 99.00th=[  523], 99.50th=[  603], 99.90th=[ 1631], 99.95th=[ 2966],
     | 99.99th=[ 8225]