The previous test was done with "noop" for scheduler (the speed test
completed at about 8MB/s). Then I rebooted the server and redone the
test (also with noop) and the result was slightly better but not as it
should be (21MB/s). A third test 5-10 minute later (after the load
subsided) completed at 16MB/s. A fourth test ended with 14.6MB/s.
Something else: the weekly auto raid check started a little time ago and
it's going at an average of 60MB/s (anywhere between 25 and 100MB/s)
with noop, cfq and deadline. A raid check with ordinary mechanical
drives gets done at about 160MB/s on the outer cylinders. Why are these
SSDs so slow?
These are the result from the 21MB/s test (5 seconds delay):
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 204.94 1918.02 389.30 1367719 277605
sdb 154.80 1196.21 389.30 853008 277605
md1 0.65 2.59 0.00 1848 0
md2 355.45 3106.05 388.53 2214890 277056
md0 1.10 2.90 0.01 2069 9
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 583.40 42764.80 29452.90 213824 147264
sdb 234.80 23172.00 14950.50 115860 74752
md1 0.00 0.00 0.00 0 0
md2 8079.60 65886.40 29862.40 329432 149312
md0 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 15.00 1.60 1740.00 8 8700
sdb 15.00 0.00 7196.80 0 35984
md1 0.00 0.00 0.00 0 0
md2 333.20 1.60 1330.40 8 6652
md0 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 167.20 538.40 37432.80 2692 187164
sdb 86.20 16.00 33688.80 80 168444
md1 0.00 0.00 0.00 0 0
md2 9510.80 572.80 37934.40 2864 189672
md0 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 150.20 585.60 29090.40 2928 145452
sdb 71.20 44.00 30355.20 220 151776
md1 0.00 0.00 0.00 0 0
md2 7306.20 615.20 28998.40 3076 144992
md0 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 257.20 1624.00 9913.80 8120 49569
sdb 137.20 372.00 21438.60 1860 107193
md1 0.00 0.00 0.00 0 0
md2 2600.80 1991.20 9504.00 9956 47520
md0 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 186.80 972.80 292.70 4864 1463
sdb 150.40 733.60 292.70 3668 1463
md1 0.00 0.00 0.00 0 0
md2 283.80 1706.40 291.20 8532 1456
md0 0.00 0.00 0.00 0 0
If you have any idea what can I do to improve this please let me know.
Thanks!!
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