I'm back here for a little question.
If I disable zfs sync : zfs set sync=disabled rpool.
my perf is perfect : 2147483648 bytes written in 0.90 seconds (2287.48 MiB/sec).
With standard zfs set sync=standard rpool :
my perf is bad : 2147483648 bytes written in 34.88 seconds (58.71 MiB/sec)...