This makes sense for some SSDs like Intel D3-4510 because they don't like overwrites of the same sector: $ fio -direct=1 -rw=write -bs=4k -size=4k -loops=100000 -iodepth=1 write: IOPS=3142, BW=12.3MiB/s (12.9MB/s)(97.9MiB/7977msec) $ fio -direct=1 -rw=write -bs=4k -size=128k -loops=100000 -iodepth=1 write: IOPS=20.8k, BW=81.4MiB/s (85.3MB/s)(543MiB/6675msec)