Linux IO Real-time monitoring Iostat command detailed

Introduction

The Iostat is primarily used to monitor the IO load on the system device, iostat the statistics from the start of the system startup when the first run, and then running Iostat displays statistics from the last time the command was run. Users can obtain the required statistics by specifying the number and time of the statistics.

Grammar

Iostat [-c] [-d] [-h] [-n] [-K |-m] [-t] [-v] [-X] [-z] [device [...] | ALL] [-p [device [,...] | all] [interval [count]]

Getting Started with

Iostat-d-K 2

The parameter-D indicates that the device (disk) usage status is displayed; k Some columns that use block are forced to use kilobytes, and 2 indicates that the data appears refreshed every 2 seconds.

The output is as follows

Iostat-d-K 1 10device:tps kb_read/s kb_wrtn/s kb_read kb_wrtnsda 39.29 21.14              1.44 441339807 29990031sda1 0.00 0.00 0.00 1623 523sda2 1.32 1.43 4.54 29834273 94827104sda3 6.30 0.85 24.95 17816289 52072524        4sda5 0.85 0.46 3.40 9543503 70970116sda6 0.00 0.00 0.00 550 236SDA7 0.00 0.00 0.00 406 0SDA8 0.00 0.            XX 0.00 406 0SDA9 0.00 0.00 0.00 406 0SDA10 60.68 18.35 71.43 383002263 1490928140device:tps kb_read/s kb_wrtn/s kb_read kb_w          RTNSDA 327.55 5159.18 102.04 5056 100sda1 0.00 0.00 0.00 0 0

The meaning of the output information

TPS: The number of transmissions per second of the device (indicate, transfers per second, were issued to the.). "One-time transfer" means "one-time I/O request". Multiple logical requests may be merged into "one I/O request". The size of the "one transfer" request is unknown. KB_READ/S: The amount of data read from the device (drive expressed) per second;
KB_WRTN/S: The amount of data written to the device (drive expressed) per second;
Kb_read: The total amount of data read, KB_WRTN: The amount of total data written, all of which are kilobytes.

In the example above, we can see statistics on the disk SDA and its partitions, when the total disk TPS for statistics is 39.29, and the following is the TPS for each partition. (because it is an instantaneous value, the total TPS is not strictly equal to the sum of each partition TPs)

Specifies that the monitored device name is SDA, and that the output of the command is exactly the same as the command above.

Iostat-d SDA 2

By default, all hard disk devices are monitored and are now designated to monitor SDA only.

- x parameter

Iostat also has a more common option- x, which will be used to display and IO-related extended data.

iostat-d-x-k 1 10Device:    rrqm/s wrqm/s   r/s   w/s rsec/s wsec/s    rkb/s    wkb/s Avgrq-sz Avgqu-sz   await  svctm  %utilsda          1.56  28.31  7.80 31.49   42.51    2.92    21.26     1.46     1.16     0.03    0.79   2.62  10.28Device:    rrqm/s wrqm/s   r/s  w/s rsec/s  wsec/s    rkb/s    wkb/s avgrq-sz avgqu-sz   await  svctm  %utilsda          2.00  20.00 381.00  7.00 12320.00  216.00  6160.00   108.00    32.31     1.75    4.50   2.17  84.20

Meaning of the output information

RRQM/S: How much of this device-dependent read request is merged per second (when the system call needs to read the data, the VFS sends the request to each FS, and if FS finds that different read requests read the same block data, FS merges the request into the merge); wrqm/ S: How much of this device-related write request per second has been merge. RSEC/S: Number of sectors read per second; wsec/: Number of sectors written per second. Rkb/s:the number of read requests that were issued to the device per second;wkb/s:the number of write requests that were I Ssued to the device per Second;avgrq-sz the average request sector size Avgqu-sz is the length of the average request queue. There is no doubt that the shorter the queue, the better.    await: The  average time (in milliseconds) of processing per IO request. This can be understood as the response time of IO, generally the system IO response time should be less than 5ms, if greater than 10ms is relatively large.         this time includes the queue time and service time, that is, in general, await is greater than SVCTM, their difference is smaller, then the shorter the queue time, conversely, the greater the difference, the longer the queue time, indicating that the system has a problem. SVCTM    represents the average service time (in milliseconds) for each device I/O operation. If the value of SVCTM is close to await, indicating that there is little I/O waiting, disk performance is good, and if the value of await is much higher than the value of SVCTM, the I/O queue waits too long for         the applications running on the system to become slower.
%util: All processing io time, divided by total statistic time, in the statistical time. For example, if the statistic interval is 1 seconds, the device has 0.8 seconds to process Io, and 0.2 seconds is idle, then the device's%util = 0.8/1 = 80%, so this parameter implies the device's busy level
。 Generally, if this parameter is 100% indicates that the device is already running close to full load (of course if it is a multi-disk, even if%util is 100% because of the concurrency of the disk, disk usage may not be the bottleneck).

- C parameter

Iostat can also be used to get CPU partial state values:

Iostat-c 1 10avg-cpu:%user%nice%sys%iowait%idle1.98 0.00 0.35 11.45 86.22avg-cpu:%user%nice%sys%iowait%idle1.62 0.00 0.25 34.46 63.67

Common usage

Iostat-d-K 1         #查看TPS和吞吐量信息 (disk read and write speed in KB) iostat-d-M 2            #查看TPS和吞吐量信息 (disk read and write speed in MB) iostat-d-x-k 1      #查看设备使 Use Rate (%util), Response time (await) Iostat-c 1 #查看cpu状态

Example Analysis

Ostat-d-K 1 |grep sda10device:            TPs    kb_read/s    kb_wrtn/s kb_read kb_wrtnsda10            60.72        18.95        71.53  395637647 1493241908sda10           299.02      4266.67       129.41       4352        132sda10           483.84      4589.90      4117.17       4544       4076sda10           218.00      3360.00       100.00       3360        100SDA10           546.00      8784.00       124.00       8784        124sda10           827.00     13232.00       136.00      13232        136

As seen above, the average number of disk transfers per second is about 400, and the disk reads about 5MB per second and writes about 1MB.

iostat-d-x-k 1Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkb/s wkb/s    Avgrq-sz Avgqu-sz   await  svctm  %utilsda          1.56  28.31  7.84 31.50   43.65    3.16    21.82     1.58     1.19     0.03    0.80   2.61  10.29SDA          1.98  24.75 419.80  6.93 13465.35  253.47  6732.67   126.73    32.15     2.00    4.70   2.00  85.25sda          3.06  41.84 444.90 54.08 14204.08 2048.98  7102.04  1024.49    32.57     2.10    4.21   1.85  92.24

You can see the average response time of the disk <5ms, and the disk usage is >80. The disk responds properly, but it is already busy.

Transfer from http://www.cnblogs.com/ggjucheng/archive/2013/01/13/2858810.html

Linux IO Real-time monitoring Iostat command detailed