linux command summary iostat command
Introduction
iostat is mainly used to monitor the IO load of system devices. When iostat runs for the first time, it displays various statistical information since the system is started. After running iostat , it will display the statistical information since the last time the command was run. The user can obtain the required statistical information by specifying the number and time of the statistics.
grammar
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iostat [ -c ] [ -d ] [ -h ] [ -N ] [ -k | -m ] [ -t ] [ -V ] [ -x ] [ -z ] [ device [...] | ALL ] [ -p [ device [,...] | ALL ] ] [ interval [ count ] ] |
Getting started
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iostat -d -k 1 10 Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn sda 39.29 21.14 1.44 441339807 29990031 sda1 0.00 0.00 0.00 1623 523 sda2 1.32 1.43 4.54 29834273 94827104 sda3 6.30 0.85 24.95 17816289 520725244 sda5 0.85 0.46 3.40 9543503 70970116 sda6 0.00 0.00 0.00 550 236 sda7 0.00 0.00 0.00 406 0 sda8 0.00 0.00 0.00 406 0 sda9 0.00 0.00 0.00 406 0 sda10 60.68 18.35 71.43 383002263 1490928140
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn sda 327.55 5159.18 102.04 5056 100 sda1 0.00 0.00 0.00 0 0 |
The parameter -d indicates that the device (disk) usage status is displayed; -k some columns that use block as the unit are forced to use Kilobytes as the unit; 2 indicates that the data display is refreshed every 2 seconds.
The meaning of the output information
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tps: The number of transfers per second that was issued to the device. (Indicate the number of transfers per second that were issued to the device.). "One transfer" means "one I/O request". Multiple logical requests may be combined 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 total amount of data written; these units are Kilobytes. |
In the above example, we can see the statistics of the disk sda and its various partitions. The total TPS of the disk at that time was 39.29 , and the following is the TPS of each partition . (Because it is an instantaneous value, the total TPS is not strictly equal to the sum of the TPS of each partition )
Specify the name of the monitored device as sda , and the output of this command is exactly the same as the above command.
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iostat -d sda 2 |
By default, all hard disk devices are monitored, and now only sda is specified .
-x parameter
iostat also has a more commonly used option -x , which will be used to display extended data related to io .
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iostat -d -x -k 1 10 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 1.56 28.31 7.80 31.49 42.51 2.92 21.26 1.46 1.16 0.03 0.79 2.62 10.28 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 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 |
输出信息的含义
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rrqm/s：每秒这个设备相关的读取请求有多少被Merge了（当系统调用需要读取数据的时候，VFS将请求发到各个FS，如果FS发现不同的读取请求读取的是相同Block的数据，FS会将这个请求合并Merge）；wrqm/s：每秒这个设备相关的写入请求有多少被Merge了。
rsec/s：每秒读取的扇区数； wsec/：每秒写入的扇区数。 rKB/s：The number of read requests that were issued to the device per second； wKB/s：The number of write requests that were issued to the device per second； avgrq-sz 平均请求扇区的大小 avgqu-sz 是平均请求队列的长度。毫无疑问，队列长度越短越好。 await： 每一个IO请求的处理的平均时间（单位是微秒毫秒）。这里可以理解为IO的响应时间，一般地系统IO响应时间应该低于5ms，如果大于10ms就比较大了。 这个时间包括了队列时间和服务时间，也就是说，一般情况下，await大于svctm，它们的差值越小，则说明队列时间越短，反之差值越大，队列时间越长，说明系统出了问题。 svctm 表示平均每次设备I/O操作的服务时间（以毫秒为单位）。如果svctm的值与await很接近，表示几乎没有I/O等待，磁盘性能很好，如果await的值远高于svctm的值，则表示I/O队列等待太长， 系统上运行的应用程序将变慢。 %util： 在统计时间内所有处理IO时间，除以总共统计时间。例如，如果统计间隔1秒，该设备有0.8秒在处理IO，而0.2秒闲置，那么该设备的%util = 0.8/1 = 80%，所以该参数暗示了设备的繁忙程度 。一般地，如果该参数是100%表示设备已经接近满负荷运行了（当然如果是多磁盘，即使%util是100%，因为磁盘的并发能力，所以磁盘使用未必就到了瓶颈）。 |
-c 参数
iostat还可以用来获取cpu部分状态值：
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iostat -c 1 10 avg-cpu: %user %nice %sys %iowait %idle 1.98 0.00 0.35 11.45 86.22 avg-cpu: %user %nice %sys %iowait %idle 1.62 0.00 0.25 34.46 63.67 |
常见用法
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iostat -d -k 1 10 #查看TPS和吞吐量信息(磁盘读写速度单位为KB) iostat -d -m 2 #查看TPS和吞吐量信息(磁盘读写速度单位为MB) iostat -d -x -k 1 10 #查看设备使用率（%util）、响应时间（await） iostat -c 1 10 #查看cpu状态 |
实例分析
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ostat -d -k 1 |grep sda10 Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn sda10 60.72 18.95 71.53 395637647 1493241908 sda10 299.02 4266.67 129.41 4352 132 sda10 483.84 4589.90 4117.17 4544 4076 sda10 218.00 3360.00 100.00 3360 100 sda10 546.00 8784.00 124.00 8784 124 sda10 827.00 13232.00 136.00 13232 136 |
上面看到，磁盘每秒传输次数平均约400；每秒磁盘读取约5MB，写入约1MB。
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iostat -d -x -k 1 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 1.56 28.31 7.84 31.50 43.65 3.16 21.82 1.58 1.19 0.03 0.80 2.61 10.29 sda 1.98 24.75 419.80 6.93 13465.35 253.47 6732.67 126.73 32.15 2.00 4.70 2.00 85.25 sda 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 |
可以看到磁盘的平均响应时间<5ms，磁盘使用率>80。磁盘响应正常，但是已经很繁忙了
引用：http://www.cnblogs.com/ginvip/p/6539393.html
细节影响成败，感谢 琴酒网络 的总结整理。