Low IO performance with disks connected to Intel SATA controller

Issue

• The IO performance on disks connected to Intel SATA controller is very low. iostat shows very high iowait values for the IO issued to these disks.

Time      %iowait Device  rrqm/s   wrqm/s   r/s   w/s    rkB/s    wkB/s  avgrq-sz  avgqu-sz   await  svctm  %util
12:53:32  20.67    sda     0.00   6366.93  0.20 48.23     0.80  24259.73  1001.81    89.61  1785.59  20.65 100.00
12:54:02  25.52    sda     0.00   6022.78  0.23 48.12     0.93  24313.55  1005.74   100.34  2050.78  20.68 100.00
12:55:10  25.46    sda     0.00   5622.72  0.18 44.69     0.71  22820.07  1017.32   103.15  2307.33  22.29 100.00
12:56:44  17.81    sda     0.00   5630.93  0.31 44.53     1.32  22605.28  1008.29   105.38  2351.34  22.30 100.00
12:58:49  18.30    sda     0.00   5750.49  0.21 45.38     0.86  23191.25  1017.33   112.00  2452.96  21.93 100.00
13:00:47  18.46    sda     0.00   5750.49  0.21 45.38     0.86  23191.25  1017.33   112.00  2452.96  21.93 100.00
13:00:47  18.46    sda     2.21   5590.00  1.58 60.90    25.22  23029.63   738.03    93.77  1517.62  15.73  98.28

• The same IO performance issues are not observed while using RHEL 6.x on the same system.