RAID0 SW gives slower ioping than each separated disk?

levnode

Hi,

I am currently running my server for some testing environment at RAID0 SW including 2 SSD disks. I have done ioping test and I found that I get better result on single disk than RAID0. Here are the results:

Single disk:

ioping /dev/sda 4 KiB <<< /dev/sda (block device 238.5 GiB): request=1 time=1.51 ms (warmup) 4 KiB <<< /dev/sda (block device 238.5 GiB): request=2 time=88.2 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=3 time=132.8 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=4 time=128.7 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=5 time=105.8 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=6 time=127.9 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=7 time=98.6 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=8 time=128.2 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=9 time=125.2 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=10 time=91.9 us 4 KiB <<< /dev/sda (block device 238.5 GiB): request=11 time=88.6 us (fast) 4 KiB <<< /dev/sda (block device 238.5 GiB): request=12 time=87.0 us (fast) ^C --- /dev/sda (block device 238.5 GiB) ioping statistics --- 11 requests completed in 1.20 ms, 44 KiB read, 9.14 k iops, 35.7 MiB/s generated 12 requests in 11.1 s, 48 KiB, 1 iops, 4.32 KiB/s min/avg/max/mdev = 87.0 us / 109.4 us / 132.8 us / 18.3 us

ioping /dev/sdb 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=1 time=216.0 us (warmup) 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=2 time=237.5 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=3 time=157.6 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=4 time=157.1 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=5 time=177.7 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=6 time=208.4 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=7 time=196.6 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=8 time=162.6 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=9 time=177.9 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=10 time=187.9 us 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=11 time=244.3 us (slow) 4 KiB <<< /dev/sdb (block device 238.5 GiB): request=12 time=197.2 us ^C --- /dev/sdb (block device 238.5 GiB) ioping statistics --- 11 requests completed in 2.10 ms, 44 KiB read, 5.23 k iops, 20.4 MiB/s generated 12 requests in 11.7 s, 48 KiB, 1 iops, 4.09 KiB/s min/avg/max/mdev = 157.1 us / 191.3 us / 244.3 us / 28.3 us

RAID0 SW:

ioping /dev/md0 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=1 time=1.65 ms (warmup) 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=2 time=1.50 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=3 time=1.59 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=4 time=1.56 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=5 time=1.58 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=6 time=1.61 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=7 time=1.61 ms (slow) 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=8 time=1.53 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=9 time=1.66 ms (slow) 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=10 time=1.61 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=11 time=1.62 ms 4 KiB <<< /dev/md0 (block device 298.7 MiB): request=12 time=1.61 ms ^C --- /dev/md0 (block device 298.7 MiB) ioping statistics --- 11 requests completed in 17.5 ms, 44 KiB read, 629 iops, 2.46 MiB/s generated 12 requests in 11.7 s, 48 KiB, 1 iops, 4.11 KiB/s min/avg/max/mdev = 1.50 ms / 1.59 ms / 1.66 ms / 42.9 us

Anyone can give me an idea? Did I make something wrong? Thank you.