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How to Check Disk Utilization on Linux with IOSTAT

linuxYou can use iostat command to check your disk utilization and monitoring sistem I/O device loading by observing the time the physical disks are active in relation to their average transfer rates.

Step 1: Install Sysstat Package

CentOS:

# yum install sysstat

Debian/Ubuntu:

# apt-get install sysstat

step 2 : iostat command for disk utilization report

iostat -d -x interval count

Description:

  • -d : Display the device utilization report (d == disk)
  • -x : Display extended statistics including disk utilization
  • interval : It is time period in seconds between two samples . iostat 2 will give data at each 2 seconds interval.
  • count : It is the number of times the data is needed . iostat 2 5 will give data at 2 seconds interval 5 times

e.g: To display 3 reports of extended statistics at 5 second intervals for disk

# iostat -d -x 5 3

output:

[[email protected] ~]# iostat -d -x 5 3
Linux 2.6.18-348.3.1.el5xen (xen.asep.us)       04/11/2013

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               4.62    26.68 29.89  6.77  3604.88   247.62   105.09     0.15    3.98   1.16   4.24
sda1              0.00     0.00  0.01  0.00     0.73     0.00   121.76     0.00    4.16   2.02   0.00
sda2              0.30     3.82  2.38  0.59   330.32    35.26   123.22     0.01    4.01   1.07   0.32
sda3              0.01     0.00  0.11  0.00    15.12     0.01   131.79     0.00    2.61   0.56   0.01
sda4              0.00     0.00  0.00  0.00     0.00     0.00     2.00     0.00    2.00   2.00   0.00
sda5              4.31    22.87 27.39  6.18  3258.71   212.35   103.40     0.13    3.98   1.19   4.00
sdb               4.19    26.68 27.97  6.77  3586.86   247.62   110.37     0.32    9.22   1.22   4.22
sdb1              0.00     0.00  0.01  0.00     0.73     0.00   122.56     0.00    3.05   1.93   0.00
sdb2              0.38     3.82  2.26  0.59   330.64    35.26   128.55     0.02    7.31   1.13   0.32
sdb3              0.01     0.00  0.11  0.00    15.10     0.01   138.45     0.00    6.10   0.54   0.01
sdb4              0.00     0.00  0.00  0.00     0.00     0.00     2.00     0.00    2.00   2.00   0.00
sdb5              3.80    22.86 25.59  6.19  3240.40   212.35   108.64     0.30    9.40   1.25   3.98
sdc               4.49    25.75 29.88  4.84  3602.92   224.71   110.21     0.13    3.87   1.15   3.99
sdc1              0.00     0.00  0.01  0.00     0.73     0.00   119.01     0.00    6.49   2.02   0.00
sdc2              0.27     3.70  2.38  0.30   329.13    32.04   135.00     0.01    4.32   1.15   0.31
sdc3              0.01     0.00  0.11  0.00    15.10     0.01   134.07     0.00    3.48   0.49   0.01
sdc4              0.00     0.00  0.00  0.00     0.00     0.00     2.00     0.00    1.00   1.00   0.00
sdc5              4.21    22.04 27.39  4.54  3257.96   192.66   108.05     0.12    3.83   1.17   3.75
sdd               4.23    25.74 28.02  4.85  3588.55   224.71   116.02     0.17    5.09   1.11   3.63
sdd1              0.00     0.00  0.01  0.00     0.73     0.00   125.99     0.00   12.05   2.12   0.00
sdd2              0.32     3.70  2.33  0.30   331.70    32.04   138.52     0.02    5.80   1.16   0.30
sdd3              0.01     0.00  0.11  0.00    15.10     0.01   134.65     0.00    5.32   0.52   0.01
sdd4              0.00     0.00  0.00  0.00     0.00     0.00     2.00     0.00    0.00   0.00   0.00
sdd5              3.90    22.04 25.58  4.55  3241.03   192.66   113.98     0.15    5.02   1.13   3.39
md1               0.00     0.00  1.39  8.19   142.05    65.54    21.66     0.00    0.00   0.00   0.00
md3               0.00     0.00 22.00 52.52   175.39   380.08     7.45     0.00    0.00   0.00   0.00
md2               0.00     0.00  0.00  0.00     0.03     0.01     8.00     0.00    0.00   0.00   0.00
md0               0.00     0.00  0.00  0.00     0.01     0.00     3.99     0.00    0.00   0.00   0.00
dm-0              0.00     0.00  3.40  3.30    27.18    26.44     8.00     0.07   10.70   0.56   0.37
dm-2              0.00     0.00  3.56  6.07    28.46    48.57     8.00     0.08    8.59   0.42   0.41
dm-4              0.00     0.00  0.99  8.14     7.91    65.15     8.00     0.08    8.32   0.45   0.41
dm-6              0.00     0.00  1.97  3.80    15.77    30.39     8.00     0.08   13.65   0.63   0.36
dm-8              0.00     0.00  0.38  7.76     2.45    21.99     3.00     0.40   48.81   0.59   0.48
dm-10             0.00     0.00  1.00  2.35     8.01    18.78     8.00     0.07   20.18   0.60   0.20
dm-12             0.00     0.00  2.07  3.69    16.59    29.54     8.00     0.07   12.77   0.46   0.27
dm-14             0.00     0.00  1.55  2.77    12.40    22.14     8.00     0.07   16.55   0.48   0.21
dm-16             0.00     0.00  1.65  4.71    13.18    37.67     8.00     0.07   11.64   0.84   0.54
dm-18             0.00     0.00  0.46  3.00     3.65    24.03     8.00     0.12   34.63   0.18   0.06
dm-20             0.00     0.00  0.13  1.50     1.02    11.98     8.00     0.06   37.64   0.15   0.02
dm-22             0.00     0.00  2.40  3.04    19.21    24.29     8.00     0.36   65.49   0.04   0.02
dm-23             0.00     0.00  2.40  2.39    19.19    19.10     8.00     0.04    7.51   0.07   0.03

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda             273.60  2391.80 2143.00 38.40 19332.80 19441.60    17.78     0.70    0.32   0.19  41.68
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.16
sda3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda5            273.60  2391.80 2143.00 38.40 19332.80 19441.60    17.78     0.70    0.32   0.19  41.44
sdb            2084.00  2384.60 306.60 45.60 19124.80 19441.60   109.50     0.25    0.71   0.52  18.32
sdb1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.16
sdb3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb5           2084.00  2384.60 306.60 45.60 19124.80 19441.60   109.50     0.25    0.71   0.52  18.16
sdc             290.00  2390.80 2316.40 26.00 20851.20 19334.40    17.16     0.65    0.28   0.17  38.96
sdc1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.16
sdc3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc5            290.00  2390.80 2316.40 26.00 20851.20 19334.40    17.16     0.65    0.28   0.17  38.96
sdd            2065.00  2384.00 120.00 32.80 17480.00 19334.40   240.93     0.26    1.67   0.97  14.80
sdd1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.16
sdd3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd5           2065.00  2384.00 120.00 32.80 17480.00 19334.40   240.93     0.26    1.67   0.96  14.64
md1               0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
md3               0.00     0.00 9598.60 4844.60 76788.80 38756.80     8.00     0.00    0.00   0.00   0.00
md2               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
dm-0              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.20  0.20     1.60     1.60     8.00     0.01   14.00  14.00   0.56
dm-4              0.00     0.00  2.40 66.60    19.20   532.80     8.00     0.30    4.34   1.59  10.96
dm-6              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-8              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-10             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-12             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-14             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-16             0.00     0.00  0.20 11.60     1.60    92.80     8.00     0.03    2.37   0.88   1.04
dm-18             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-20             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-22             0.00     0.00 4817.40  0.60 38539.20     4.80     8.00    14.58    3.03   0.02  11.68
dm-23             0.00     0.00 4778.40 4765.60 38227.20 38124.80     8.00    77.06    8.07   0.07  63.52

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda             634.80  2161.00 1801.60 55.00 19491.20 17728.00    20.05     0.85    0.46   0.26  47.92
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda2              0.00     0.00  0.00  2.20     0.00    17.60     8.00     0.04   18.55  13.45   2.96
sda3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda5            634.80  2161.00 1801.60 52.80 19491.20 17710.40    20.06     0.81    0.44   0.25  47.28
sdb            1438.20  2156.80 378.20 59.20 14531.20 17728.00    73.75     0.30    0.69   0.49  21.52
sdb1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb2              0.00     0.00  0.00  2.20     0.00    17.60     8.00     0.02    8.73   8.00   1.76
sdb3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdb5           1438.20  2156.80 378.20 57.00 14531.20 17710.40    74.08     0.28    0.65   0.47  20.64
sdc             540.00  2156.00 1949.20 44.80 19913.60 17606.40    18.82     0.70    0.35   0.22  44.08
sdc1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc2              0.00     1.40  0.00  1.20     0.00    20.80    17.33     0.01   11.33  10.00   1.20
sdc3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdc5            540.00  2154.60 1949.20 43.60 19913.60 17585.60    18.82     0.69    0.35   0.22  43.36
sdd            1529.00  2153.20 246.80 47.60 14206.40 17606.40   108.06     0.34    1.17   0.70  20.56
sdd1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd2              0.00     1.40  0.00  1.20     0.00    20.80    17.33     0.01    6.67   5.33   0.64
sdd3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd4              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sdd5           1529.00  2151.80 246.80 46.40 14206.40 17585.60   108.43     0.34    1.14   0.68  19.92
md1               0.00     0.00  0.00  3.20     0.00    25.60     8.00     0.00    0.00   0.00   0.00
md3               0.00     0.00 8518.00 4410.40 68144.00 35283.20     8.00     0.00    0.00   0.00   0.00
md2               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
dm-0              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-4              0.00     0.00  7.40 246.40    59.20  1971.20     8.00     1.45    5.70   1.34  33.92
dm-6              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-8              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-10             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-12             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-14             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-16             0.00     0.00  0.40 22.20     3.20   177.60     8.00     0.08    3.50   1.06   2.40
dm-18             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-20             0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-22             0.00     0.00 4253.80  0.60 34030.40     4.80     8.00    16.39    3.85   0.03  13.20
dm-23             0.00     0.00 4256.80 4141.20 34054.40 33129.60     8.00    69.49    8.28   0.08  65.84

Decription the output above:

  • rrqm/s : The number of read requests merged per second that were queued to the hard disk
  • wrqm/s : The number of write requests merged per second that were queued to the hard disk
  • r/s : The number of read requests per second
  • w/s : The number of write requests per second
  • rsec/s : The number of sectors read from the hard disk per second
  • wsec/s : The number of sectors written to the hard disk per second
  • avgrq-sz : The average size (in sectors) of the requests that were issued to the device.
  • avgqu-sz : The average queue length of the requests that were issued to the device
  • await : The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by the requests in queue and the time spent servicing them.
  • svctm : The average service time (in milliseconds) for I/O requests that were issued to the device
  • %util : Percentage of CPU time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100%.

How do I interpret the output result for optimization?

First you need to note down following values from the iostat output:

  • The average service time (svctm)
  • Percentage of CPU time during which I/O requests were issued (%util)
  • See if a hard disk reports consistently high reads/writes (r/s and w/s)

If any one of these are high, you need to take one of the following action:

  • Get high speed disk and controller for file system (for example move from SATA I to SAS 15k disk)
  • Tune software or application or kernel or file system for better disk utilization
  • Use RAID array to spread the file system

source: http://www.cyberciti.biz/tips/how-do-i-find-out-linux-cpu-utilization.html

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