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This article will explain in detail how to check the disk IO status in linux. The content of the article is of high quality, so the editor will share it for you as a reference. I hope you will have some understanding of the relevant knowledge after reading this article.

Iostat result analysis

[kefu@SZ-8 linux] $iostat-x-k

Linux 2.6.18-128.el5_cyou_1.0 (SZ-8.30) 09Unix 08 Universe 2011

Avg-cpu:% user nice% system% iowait% steal% idle

16.58 0.00 2.79 0.46 0.00 80.16

Device: rrqm/s wrqm/s rUnip s wdeband s rkB/s wkB/s avgrq-sz avgqu-sz await svctm% util

Sda 0.06 29.28 0.22 37.14 10.21 265.68 14.77 0.02 0.51 0.15 0.55

Sda1 0.00 0.00 0.00 10.79 0.00 2.66 2.43 0.00

Sda2 0.01 0.78 0.10 0.36 0.81 4.58 23.51 0.00 1.21 0.84 0.04

Sda3 0.03 15.17 0.09 35.39 8.98 202.24 11.91 0.01 0.26 0.12 0.44

Sda4 0.00 0.00 0.00 2.00 0.00 33.33 33.33 0.00

Sda5 0.01 1.59 0.03 0.51 0.34 8.40 32.20 0.00 1.19 0.58 0.03

Sda6 0.00 0.00 0.00 0.12 0.00 0.48 8.18 0.00 5.02 4.53 0.05

Sda7 0.00 0.00 0.00 45.00 0.00 5.52 3.04 0.00

Sda8 0.00 0.00 0.00 40.88 0.00 7.62 6.03 0.00

Sda9 0.00 0.00 0.00 39.71 0.00 7.37 5.83 0.00

Sda10 0.00 0.00 0.00 37.57 0.00 5.70 3.54 0.00

Sda11 0.00 11.74 0.01 0.76 0.08 49.97 131.48 0.01 10.74 0.57 0.04

Sdb 0.01 3.91 20.24 20.21 1262.95 1853.94 154.09 0.52 12.84 1.97 7.95

Rrqm/s: the number of merge reads per second. Namely delta (rmerge) / s

Wrqm/s: the number of merge writes per second. Namely delta (wmerge) / s

Rdyne s: the number of times the read of the Iripple O device was completed per second. Namely delta (rio) / s

Whand s: the number of times the write I _ hand 0 device has been completed per second. Namely delta (wio) / s

Rsec/s: read sectors per second. Namely delta (rsect) / s

Wsec/s: the number of sectors written per second. Namely delta (wsect) / s

RKB/s: read K bytes per second. Is half the size of rsec/s because each sector size is 512 bytes

WKB/s: write K bytes per second. It's half of wsec/s.

Avgrq-sz: the average data size (sector) per device Istroke O operation. That is, delta (rsect+wsect) / delta (rio+wio)

Avgqu-sz: average Imax O queue length. That is, delta (aveq) / aveq 1000 (because it is in milliseconds)

Await: the average wait time (in milliseconds) for each device Istroke O operation. That is, delta (ruse+wuse) / delta (rio+wio)

Svctm: the average service time (in milliseconds) for each device Istroke O operation. That is, delta (use) / delta (rio+wio)

% util: how many percent of the time in a second is spent on the Imax O operation, or how much time in a second the Ipicuro queue is not empty. That is, delta (usr) / use 1000 (because it is in milliseconds)

If the% util is close to 100%, it means that too many requests have been generated, the system is fully loaded, and there may be a bottleneck on the disk.

More important parameters

% util: how many percent of the time in a second is spent on the Imax O operation, or how much time in a second when the Ipicuro queue is not empty

Svctm: the average service time for each device Istroke O operation

Await: average waiting time for each device Istroke O operation

Avgqu-sz: average Imax O queue length

If the% util is close to 100%, it means that there are too many wait requests, the system is fully loaded, and there may be bottlenecks on the disk. Generally, the pressure is greater when the% util is greater than 70%, and the read speed has more wait.

At the same time, you can check the b parameter (the number of processes waiting for resources) and the wa parameter (the percentage of CPU time spent waiting by vmstat, which is higher than 30% when the pressure is high).

The size of the await generally depends on the service time (svctm) as well as the length of the Imax O queue and the mode in which the Imax O request is issued. If svctm is close to await, it means that there is almost no waiting time; if

The await is much larger than the svctm, which means that the Iamp O queue is too long, and the response time of the application becomes slower.

The metaphor of image

R/s+w/s is similar to the total number of payers

The average queue length (avgqu-sz) is similar to the average number of people queued per unit time

The average service time (avctm) is similar to the cashier's speed of collection.

The average waiting time (await) is similar to the average waiting time per person.

The average avgrq-sz is similar to what the average person buys.

The% util is similar to the percentage of time someone queued in front of the cashier.

Svctm is generally less than await (because the waiting time of requests waiting at the same time is double-counted), the size of svctm is generally related to disk performance, the load of CPU/ memory will also affect it, and too many requests will

Indirectly lead to the increase of svctm. The size of the await generally depends on the service time (svctm) as well as the length of the Imax O queue and the mode in which the Imax O request is issued. If svctm is close to await, it means that there are almost no IMaple O

Wait time; if await is much larger than svctm, it means that the response time obtained by the application becomes slower because the Imax O queue is too long. If the response time exceeds the range allowed by the user, you can consider replacing a faster disk and adjusting the

Whole kernel elevator algorithm, optimize applications, or upgrade CPU

Queue length (avcqu-sz) can also be used as an index to measure the load of the system, but because the avcqu-sz is according to the average per unit time, it can not reflect the instantaneous flood.

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