LSI SAS 2308 MPT2SAS Desempenho de leitura / gravação do Linux

Question

Placa PCIe 3.0 LSI SAS 2308-8e (6Gb / s por faixa). Média Leitura / Gravação O desempenho bruto para 4 SSDs é muito baixo, cerca de 430 MB / s (Esperado 2 GB / s). Tenho um Intel Core i3 com quad-core e 4 GB de RAM.

xdd.linux -op write -targets 4 /dev/sdb /dev/sdc /dev/sdd /dev/sde -blocksize 512 -reqsize 2048 -mbytes 10240 -passes 1 -queuedepth 32 -verbose -dio
TARGET   PASS0001    0 32   10737418240    10240   101.778   105.499     100.61    0.0099     0.01   write     1048576 
TARGET   PASS0001    1 32   10737418240    10240   101.789   105.487     100.60    0.0099     0.01   write     1048576 
TARGET   PASS0001    2 32   10737418240    10240   101.786   105.490     100.60    0.0099     0.01   write     1048576 
TARGET   PASS0001    3 32   10737418240    10240   101.788   105.488     100.60    0.0099     0.01   write     1048576 
TARGET   Average     0 32   10737418240    10240   101.778   105.499     100.61    0.0099     0.01   write     1048576 
TARGET   Average     1 32   10737418240    10240   101.789   105.487     100.60    0.0099     0.01   write     1048576 
TARGET   Average     2 32   10737418240    10240   101.786   105.490     100.60    0.0099     0.01   write     1048576 
TARGET   Average     3 32   10737418240    10240   101.788   105.488     100.60    0.0099     0.01   write     1048576 
         Combined    4 128   42949672960    40960   101.789   421.948     402.40    0.0025     0.04   write     1048576 

 cat /proc/interrupts
 43:     260472          0          0          0   PCI-MSI-edge      mpt2sas0-msix0
 44:         12     210300          0          0   PCI-MSI-edge      mpt2sas0-msix1
 45:       1287          0          0          0   PCI-MSI-edge      mpt2sas0-msix2
 46:          2       1199          0          0   PCI-MSI-edge      mpt2sas0-msix3

cat /proc/irq/43/smp_affinity
5
cat /proc/irq/44/smp_affinity
a
cat /proc/irq/45/smp_affinity
5
cat /proc/irq/46/smp_affinity
a

Alguma idéia de por que estamos tendo menos desempenho do que o esperado?