Other Mystery SSD 4k unaligned issue

[adam1997]

hi guys

I meet a unexplaineable problem

I have 2 PCIe SSD card which are in the same type



I do some fio test:

SSD1:

fio -runtime=300 -ramp_time=0 -numjobs=1 -iodepth=32 -direct=1 -sync=0 -thread -time_based -zero_buffers -buffered=1 -ioengine=posixaio -rw=randread -bs=128k -name=rand_read -size=100g -filename=/dev/nvd0

the iostat shows that

no align
device r/s w/s kr/s kw/s ms/r ms/w ms/o ms/t qlen %b
nvd0     11486.7   0.0 1470291.7     0.0   31   2.5 100

fio -runtime=300 -ramp_time=0 -numjobs=1 -iodepth=32 -direct=1 -sync=0 -thread -time_based -zero_buffers -buffered=1 -ioengine=posixaio -rw=randread -bs=128k -name=rand_read -size=100g -filename=/dev/nvd0 -blockalign=4k

I add a blockalign option: blockalign=4k
the iostat shows that

device r/s w/s kr/s kw/s ms/r ms/w ms/o ms/t qlen %b
nvd0      1575.4   0.0  201653.5     0.0   28  19.0 100

SSD2:

fio -runtime=300 -ramp_time=0 -numjobs=1 -iodepth=32 -direct=1 -sync=0 -thread -time_based -zero_buffers -buffered=1 -ioengine=posixaio -rw=randread -bs=128k -name=rand_read -size=100g -filename=/dev/nvd0

the iostat shows that

device r/s w/s kr/s kw/s ms/r ms/w ms/o ms/t qlen %b
nvd0 10832 0 1386544.0 0.0 2 0 0 2 32 100

fio -runtime=300 -ramp_time=0 -numjobs=1 -iodepth=32 -direct=1 -sync=0 -thread -time_based -zero_buffers -buffered=1 -ioengine=posixaio -rw=randread -bs=128k -name=rand_read -size=100g -filename=/dev/nvd0 -blockalign=4k

I add a blockalign blockalign=4k
the iostat shows that

device r/s w/s kr/s kw/s ms/r ms/w ms/o ms/t qlen %b
nvd0 11131 0 1424882.1 0.0 2 0 0 2 32 100

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adding blockalign has a big difference for SSD1

but SSD2 do not have significant performance degrade

does anyone has any ideas?