On 2014-04-15 17:04, Xiaofei Du wrote:
[global] bs=4k size=100m direct=1 filename=100mfile [seq-write] rw=write stonewall [rand-write] rw=randwrite stonewall ######################################################################## This is the output. In this run the difference is 115 vs 123. On another disk, the number I got was 121 vs 141. Random writes are always faster than sequential writes.
Since the region is only 100M, it seems reasonable to expect random IO within that region to be faster than sequential ones. The sequential ones will always be subject to a full rotational penalty, limiting your IOPS to 120 if we disregard software overhead, DMA, etc. So 115 seems very in the ballpark. For random IO, we have to move the head a bit, but if the seek is less than half 1/RPM, then it's a win.
So I'd say things are looking as expected. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
