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
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