IO performance symptoms


 
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Special Forums Hardware Filesystems, Disks and Memory IO performance symptoms
# 1  
Old 08-17-2009
IO performance symptoms

Hello,
Does anyone have a good link which outlines symptoms for different performance issues related to IO? I am looking for data I can compare to my IOSTAT or VMSTAT output. For example, I am trying to see if my disk is thrashing..does anyone have output on vmstat or iostat from when there disk was thrashing..
# 2  
Old 08-17-2009
would be more helpfull if you post your output and try to explain where your problems are...
# 3  
Old 08-18-2009
Vada,

disks are only thrashing when you are very low in memory and your systems is permanently paging in and out.

Disks being busy up to 70% is normal on AIX and no reason for concern ... are you trying to investigate high IO waits from cpu? What kind of applications do you run?

I agree with DukeNuke, it would be more helpful if we could see your stats to tell you more than fishing in the dark.

Rgds
zxmaus
# 4  
Old 08-24-2009
Stats are posted below.

IOSTAT:
Code:
avg-cpu:  %user   %nice    %sys %iowait   %idle
           0.75    0.00    3.33   22.56   73.36

Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await  svctm  %util
sda         38.00  59.33 500.00 12.33 19373.33  573.33  9686.67   286.67    38.93     1.52    2.96   1.76  90.00
sdb          0.00  76.67  1.00 39.33    5.33  760.00     2.67   380.00    18.98     2.73  634.89   3.41  13.77

avg-cpu:  %user   %nice    %sys %iowait   %idle
           1.08    0.00    4.41   28.73   65.78

Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await  svctm  %util
sda         20.33   0.00 506.00  0.67 25728.00    5.33 12864.00     2.67    50.79     1.29    2.55   1.88  95.40
sdb          0.00 4528.33  0.00 89.33    0.00 36949.33     0.00 18474.67   413.61    43.44  486.30   4.16  37.20

MPSTAT:
Code:
04:00:20 AM  CPU   %user   %nice %system %iowait    %irq   %soft   %idle    intr/s
04:00:21 AM  all    2.50    0.00    5.75   21.00    0.00    0.00   70.75   2102.02
04:00:22 AM  all    0.00    0.00    1.75   23.31    0.00    0.25   74.69   1784.00
04:00:23 AM  all    0.50    0.00    2.49   22.94    0.25    0.00   73.82   1779.00
Average:     all    1.00    0.00    3.33   22.42    0.08    0.08   73.08   1887.63

VMSTAT:
Code:
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
12  2 1416976  45892 423720 12917860    0    0    16    28    1     1  1  1 98  0
 0  1 1416976  24188 424548 12941932    0   92 14264   656 2082  4831  3  6 71 21
 0  1 1417020  20924 424868 12945332    0  484  8136  1344 1785  4556  0  2 75 23

SAR -B:
Code:
03:30:01 AM  pgpgin/s pgpgout/s   fault/s  majflt/s
03:40:01 AM      0.38     41.41   3438.90      0.01
03:50:01 AM      0.09     47.06   3719.47      0.00
04:00:01 AM   1811.48   2079.85   3900.20      0.01
Average:       603.94    722.73   3686.15      0.01

04:02:40 AM       LINUX RESTART


Last edited by vada010; 08-24-2009 at 10:21 PM..
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