Low IOPS de gravação SSD (~ 100)

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Estou com IOPS muito baixo com um SSD no meu servidor. Notei isso ao executar um servidor de banco de dados mysql, que teve um desempenho muito ruim quando havia muitas atualizações (~ 100 por segundo) em um banco de dados InnoDB.

Aqui estão as especificações do servidor:

SSD: Modelo = Samsung SSD 850 EVO 120 GB, FwRev = EMT01B6Q

Servidor: HP proliant DL320e Gen8

CPU: CPU Intel (R) Xeon (R) E3-1270 v3 a 3,50GHz

SO: Ubuntu 14.04.1 LTS

Kernel: Linux h119 3.13.0-44-genérico # 73-Ubuntu SMP Ter Dez 16 00:22:43 UTC 2014 x86_64 x86_64 x86_64 GNU / Linux

Ao verificar o SSD enquanto há alguma carga nele, estou obtendo esses resultados com iostat -kx 1 20 

root@h119:~# iostat -kx 1 20
Linux 3.13.0-44-generic (h119)  02/19/2015      _x86_64_        (8 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.14    0.00    0.08    1.06    0.00   98.72

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               5.14    14.75    0.80   17.68   378.51   258.59    68.94     0.22   12.03    1.76   12.50   7.90  14.60
sdb               0.00    19.89    0.00   18.44     0.05   636.16    68.99     0.26   14.32    0.43   14.33   8.22  15.17
md2               0.00     0.00    0.04   31.40     0.97   257.88    16.46     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     7.93     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     8.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.00    0.00    0.63    1.00    0.00   97.37

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    21.00    0.00   18.00     0.00   346.00    38.44     0.19   10.44    0.00   10.44   7.78  14.00
sdb               0.00    21.00    0.00   18.00     0.00   346.00    38.44     0.18   10.00    0.00   10.00   7.33  13.20
md2               0.00     0.00    0.00   36.00     0.00   356.00    19.78     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.25    0.00    0.75    1.50    0.00   96.50

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    19.00    0.00   19.00     0.00   218.00    22.95     0.20    9.47    0.00    9.47   9.89  18.80
sdb               0.00    19.00    0.00   19.00     0.00   218.00    22.95     0.20    9.68    0.00    9.68  10.11  19.20
md2               0.00     0.00    0.00   37.00     0.00   236.00    12.76     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.75    0.00    1.12    1.37    0.00   95.76

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    19.80    0.00   16.83     0.00   291.09    34.59     0.19    9.88    0.00    9.88   9.18  15.45
sdb               0.00    19.80    0.00   16.83     0.00   291.09    34.59     0.19    9.88    0.00    9.88   9.18  15.45
md2               0.00     0.00    0.00   35.64     0.00   336.63    18.89     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.00    0.00    0.75    1.00    0.00   97.25

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    18.00    0.00   22.00     0.00   310.00    28.18     0.16    8.91    0.00    8.91   6.36  14.00
sdb               0.00    18.00    0.00   22.00     0.00   310.00    28.18     0.16    9.09    0.00    9.09   6.55  14.40
md2               0.00     0.00    0.00   32.00     0.00   228.00    14.25     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.75    0.00    0.75    1.00    0.00   97.50

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    10.00    0.00   13.00     0.00   142.00    21.85     0.13    9.85    0.00    9.85   9.85  12.80
sdb               0.00    10.00    0.00   13.00     0.00   142.00    21.85     0.12    9.54    0.00    9.54   9.54  12.40
md2               0.00     0.00    0.00   19.00     0.00   140.00    14.74     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.26    0.00    0.88    1.26    0.00   96.61

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    34.00    0.00   12.00     0.00   333.00    55.50     0.12   10.00    0.00   10.00  10.33  12.40
sdb               0.00    34.00    0.00   12.00     0.00   333.00    55.50     0.12   10.00    0.00   10.00  10.33  12.40
md2               0.00     0.00    0.00   45.00     0.00   352.00    15.64     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.37    0.00    0.87    1.50    0.00   96.26

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    17.00    0.00   28.00     0.00   713.00    50.93     0.28   10.00    0.00   10.00   5.86  16.40
sdb               0.00    17.00    0.00   28.00     0.00   713.00    50.93     0.27    9.86    0.00    9.86   5.71  16.00
md2               0.00     0.00    0.00   43.00     0.00   692.00    32.19     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.50    0.00    0.75    1.38    0.00   96.37

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    35.00    0.00   20.00     0.00   361.00    36.10     0.18    9.20    0.00    9.20   8.00  16.00
sdb               0.00    35.00    0.00   20.00     0.00   361.00    36.10     0.18    9.20    0.00    9.20   8.00  16.00
md2               0.00     0.00    0.00   53.00     0.00   360.00    13.58     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.25    0.00    1.12    1.12    0.00   96.50

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    20.00    0.00   11.00     0.00   193.00    35.09     0.11    9.82    0.00    9.82   9.82  10.80
sdb               0.00    20.00    0.00   11.00     0.00   193.00    35.09     0.11   10.18    0.00   10.18  10.18  11.20
md2               0.00     0.00    0.00   29.00     0.00   192.00    13.24     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.00    0.00    0.50    0.62    0.00   97.88

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    12.00    0.00    9.00     0.00   137.00    30.44     0.09    9.78    0.00    9.78   8.44   7.60
sdb               0.00    12.00    0.00    9.00     0.00   137.00    30.44     0.09   10.22    0.00   10.22   8.89   8.00
md2               0.00     0.00    0.00   19.00     0.00   136.00    14.32     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.13    0.00    0.63    0.63    0.00   97.62

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    15.00    0.00    8.00     0.00   181.00    45.25     0.08   10.00    0.00   10.00  10.00   8.00
sdb               0.00    15.00    0.00    8.00     0.00   181.00    45.25     0.07    9.00    0.00    9.00   9.00   7.20
md2               0.00     0.00    0.00   25.00     0.00   244.00    19.52     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.88    0.00    0.63    0.88    0.00   97.60

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    28.00    0.00   15.00     0.00   301.00    40.13     0.14    9.33    0.00    9.33   6.93  10.40
sdb               0.00    28.00    0.00   15.00     0.00   301.00    40.13     0.14    9.33    0.00    9.33   6.93  10.40
md2               0.00     0.00    0.00   38.00     0.00   236.00    12.42     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.75    0.00    1.25    0.50    0.00   97.50

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    15.00    0.00    7.00     0.00   177.00    50.57     0.08    9.71    0.00    9.71  10.86   7.60
sdb               0.00    15.00    0.00    7.00     0.00   177.00    50.57     0.07    9.14    0.00    9.14  10.29   7.20
md2               0.00     0.00    0.00   22.00     0.00   188.00    17.09     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.76    0.00    0.38    1.13    0.00   97.73

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    17.00    0.00   17.00     0.00   205.00    24.12     0.16    9.65    0.00    9.65   7.06  12.00
sdb               0.00    17.00    0.00   17.00     0.00   205.00    24.12     0.16    9.65    0.00    9.65   7.06  12.00
md2               0.00     0.00    0.00   33.00     0.00   196.00    11.88     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.38    0.00    0.63    0.88    0.00   97.11

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    19.00    0.00   11.00     0.00   245.00    44.55     0.10    9.45    0.00    9.45   9.45  10.40
sdb               0.00    19.00    0.00   11.00     0.00   245.00    44.55     0.10    9.45    0.00    9.45   9.45  10.40
md2               0.00     0.00    0.00   28.00     0.00   244.00    17.43     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.76    0.00    0.50    1.39    0.00   97.35

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    28.00    0.00   20.00     0.00   305.00    30.50     0.19    9.40    0.00    9.40   8.60  17.20
sdb               0.00    28.00    0.00   20.00     0.00   305.00    30.50     0.19    9.40    0.00    9.40   8.60  17.20
md2               0.00     0.00    0.00   47.00     0.00   304.00    12.94     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.01    0.00    0.63    1.13    0.00   97.23

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    28.00    0.00   16.00     0.00   357.00    44.62     0.15    9.75    0.00    9.75   8.50  13.60
sdb               0.00    28.00    0.00   16.00     0.00   357.00    44.62     0.15    9.50    0.00    9.50   8.25  13.20
md2               0.00     0.00    0.00   44.00     0.00   356.00    16.18     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.13    0.00    0.75    1.50    0.00   96.62

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    19.00    0.00   22.00     0.00   297.00    27.00     0.19    8.91    0.00    8.91   5.82  12.80
sdb               0.00    19.00    0.00   22.00     0.00   297.00    27.00     0.22   10.36    0.00   10.36   6.36  14.00
md2               0.00     0.00    0.00   40.00     0.00   296.00    14.80     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.13    0.00    0.75    1.13    0.00   96.99

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00    23.00    0.00   18.00     0.00   313.00    34.78     0.19   10.22    0.00   10.22   7.78  14.00
sdb               0.00    23.00    0.00   18.00     0.00   313.00    34.78     0.19   10.22    0.00   10.22   7.78  14.00
md2               0.00     0.00    0.00   39.00     0.00   312.00    16.00     0.00    0.00    0.00    0.00   0.00   0.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

O resultado a seguir é com fio --rw = write --name = teste --size = 20M --direct = 1 

root@h119:~# fio --rw=write --name=test --size=20M --direct=1
test: (g=0): rw=write, bs=4K-4K/4K-4K/4K-4K, ioengine=sync, iodepth=1
fio-2.1.3
Starting 1 process
test: Laying out IO file(s) (1 file(s) / 20MB)
Jobs: 1 (f=1): [W] [100.0% done] [0KB/404KB/0KB /s] [0/101/0 iops] [eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=11288: Sat Feb 21 19:59:52 2015
  write: io=20480KB, bw=415022B/s, iops=101, runt= 50531msec
    clat (usec): min=9674, max=21523, avg=9867.58, stdev=615.15
     lat (usec): min=9675, max=21524, avg=9867.76, stdev=615.16
    clat percentiles (usec):
     |  1.00th=[ 9792],  5.00th=[ 9792], 10.00th=[ 9792], 20.00th=[ 9792],
     | 30.00th=[ 9792], 40.00th=[ 9792], 50.00th=[ 9792], 60.00th=[ 9792],
     | 70.00th=[ 9792], 80.00th=[ 9792], 90.00th=[ 9920], 95.00th=[10048],
     | 99.00th=[12480], 99.50th=[12864], 99.90th=[18304], 99.95th=[18560],
     | 99.99th=[21632]
    bw (KB  /s): min=  380, max=  411, per=100.00%, avg=405.33, stdev= 5.11
    lat (msec) : 10=90.66%, 20=9.32%, 50=0.02%
  cpu          : usr=0.03%, sys=0.19%, ctx=5138, majf=0, minf=26
  IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     issued    : total=r=0/w=5120/d=0, short=r=0/w=0/d=0

Run status group 0 (all jobs):
  WRITE: io=20480KB, aggrb=405KB/s, minb=405KB/s, maxb=405KB/s, mint=50531msec, maxt=50531msec

Disk stats (read/write):
    md2: ios=0/5580, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=0/5379, aggrmerge=0/191, aggrticks=0/52640, aggrin_queue=52640, aggrutil=99.00%
  sda: ios=0/5379, merge=0/191, ticks=0/52508, in_queue=52508, util=98.63%
  sdb: ios=0/5379, merge=0/191, ticks=0/52772, in_queue=52772, util=99.00%

Como você pode ver, as IOPS estão em 101, e eu posso escrever apenas 404kB / seg. Além disso, não há muita flutuação na IOPS enquanto a ferramenta está em execução, é sempre entre 101 e 103.

Eu também confio nos resultados do fio, pois meu banco de dados fica lento quando atinge cerca de 100 atualizações / inserções por segundo.

Com um servidor idêntico (hardware e software) e sem RAID, recebo exatamente os mesmos resultados, portanto, isso não pode ser devido ao software RAID: 

root@h073:~# fio --rw=write --name=test --size=20M --direct=1
test: (g=0): rw=write, bs=4K-4K/4K-4K/4K-4K, ioengine=sync, iodepth=1
fio-2.1.3
Starting 1 process
Jobs: 1 (f=1): [W] [100.0% done] [0KB/408KB/0KB /s] [0/102/0 iops] [eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=15147: Sat Feb 21 20:52:14 2015
  write: io=20480KB, bw=418492B/s, iops=102, runt= 50112msec
    clat (usec): min=1504, max=17337, avg=9785.74, stdev=417.14
     lat (usec): min=1504, max=17337, avg=9785.93, stdev=417.13
    clat percentiles (usec):
     |  1.00th=[ 9792],  5.00th=[ 9792], 10.00th=[ 9792], 20.00th=[ 9792],
     | 30.00th=[ 9792], 40.00th=[ 9792], 50.00th=[ 9792], 60.00th=[ 9792],
     | 70.00th=[ 9792], 80.00th=[ 9792], 90.00th=[ 9792], 95.00th=[ 9792],
     | 99.00th=[12480], 99.50th=[12608], 99.90th=[13120], 99.95th=[15040],
     | 99.99th=[17280]
    bw (KB  /s): min=  400, max=  416, per=100.00%, avg=408.75, stdev= 2.69
    lat (msec) : 2=0.04%, 4=0.04%, 10=98.14%, 20=1.78%
  cpu          : usr=0.04%, sys=0.12%, ctx=5132, majf=0, minf=27
  IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     issued    : total=r=0/w=5120/d=0, short=r=0/w=0/d=0

Run status group 0 (all jobs):
  WRITE: io=20480KB, aggrb=408KB/s, minb=408KB/s, maxb=408KB/s, mint=50112msec, maxt=50112msec

Disk stats (read/write):
  sda: ios=0/5132, merge=0/43, ticks=0/50048, in_queue=50048, util=99.52%

O que é notável é que a velocidade é muito constante a 404kB / s em 101-103 IOPS.

Copiar arquivos, no entanto, é muito rápido e satisfaz minhas expectativas para um SSD: 

root@h119:~# dd if=randomfile of=randomfile2
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 2.27684 s, 472 MB/s

Portanto, parece que somente as gravações aleatórias de 4k são lentas como o inferno. Se você precisar de mais alguma informação, avise-me e atualizarei. Agradecemos antecipadamente pela sua resposta.

Atualização: O problema não persiste mais em um servidor que não é da HP. Por isso, deve haver algo para fazer como os servidores da HP acessam o SSD. No outro hardware eu recebo os seguintes resultados, que são perfeitamente bem: 

root@ca286:~# fio --rw=write --name=test --size=40M --direct=1
test: (g=0): rw=write, bs=4K-4K/4K-4K/4K-4K, ioengine=sync, iodepth=1
fio-2.1.3
Starting 1 process
test: Laying out IO file(s) (1 file(s) / 40MB)

test: (groupid=0, jobs=1): err= 0: pid=1285: Wed Feb 25 20:47:25 2015
  write: io=40960KB, bw=130032KB/s, iops=32507, runt=   315msec
    clat (usec): min=24, max=1588, avg=30.34, stdev=15.59
     lat (usec): min=24, max=1589, avg=30.39, stdev=15.60
    clat percentiles (usec):
     |  1.00th=[   26],  5.00th=[   29], 10.00th=[   29], 20.00th=[   30],
     | 30.00th=[   30], 40.00th=[   30], 50.00th=[   30], 60.00th=[   30],
     | 70.00th=[   30], 80.00th=[   31], 90.00th=[   31], 95.00th=[   31],
     | 99.00th=[   33], 99.50th=[   54], 99.90th=[   56], 99.95th=[   56],
     | 99.99th=[  114]
    lat (usec) : 50=99.30%, 100=0.68%, 250=0.01%
    lat (msec) : 2=0.01%
  cpu          : usr=2.55%, sys=18.47%, ctx=10247, majf=0, minf=26
  IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     issued    : total=r=0/w=10240/d=0, short=r=0/w=0/d=0

Run status group 0 (all jobs):
  WRITE: io=40960KB, aggrb=130031KB/s, minb=130031KB/s, maxb=130031KB/s, mint=315msec, maxt=315msec

Disk stats (read/write):
  sda: ios=0/4806, merge=0/0, ticks=0/120, in_queue=120, util=48.19%
    
por Hook 21.02.2015 / 21:15

1 resposta

1

Fizemos a mesma observação em nossos testes com SSD no Gen7, mas acho que a diferença para o Gen8 não é muito grande.

Se você conectar o SSD diretamente à placa, o desempenho é como seria de esperar (os servidores ProLiant têm apenas uma porta para aquela em que a unidade de DVD está conectada por padrão).

Se você conectar o SSD através do RAID Controller, não importa se você configurou nenhum RAID (Jbod), ele ficará lento, contanto que os dados tenham que passar pelo Controlador, o desempenho é ruim. Nós achamos que tem a ver com o controlador não construir para drives tão rápido.

Se você comprar HP SSDs e colocá-los nesses servidores, seu desempenho ficará melhor (por causa de uma melhor comunicação entre Controlador e Disco), mas nem de longe o desempenho anunciado (~ 20% disso).

Portanto, o ProLiants Gen7 / 8 SAS Controller, simplesmente não é feito para SSDs. Seria interessante que esse gargalo ainda existisse com o Gen9, pois dessa forma você só pode conectar um disco via SlimSATA a um Gen7 / Gen8 (e isso apenas via colocar o disco no chassi e não nos slots)

    
por 19.11.2015 / 11:40

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