Iostat Command detailed--linux performance analysis

Before summarizing uptime and the free command, continue today to summarize the iostat. Leave a note for yourself, and also hope to be useful to everyone.

Version information:

Sysstat version 9.0.4
(C) Sebastien Godard (Sysstat <at> orange.fr)

Basic use:

Iostat [-c] [-d] [-n] [-n] [-h] [-K |-m] [-t] [-v] [-X] [-z] [device [...] | ALL] [-p [device [,...] | ALL] [Inter-val [Count]]

[-c]: Output CPU statistics

[-d]: Output disk statistics Note: The default is two outputs

[-n]: Output IO information according to device Mapper, which is what we often call LVM

[-n]: Output IO information based on network file system (NFS) (Kernel version> 2.6.17)

[-h]: Better readability of NFS statistics

[-K |-m]: replace original block/s with kb/s|mb/s

[-T]: print time to collect information at the moment Note: Time printing format and system variable S_time_format related

[-V]: version information

[-X]: Output Expansion Statistics Note: summary below

[-z]: RESET disk input/output information

[Device [...] | ALL]: Device list

[-P [device[...]| ALL]]: Device list, but this will output the IO information of the sub-device. such as SDB, it will even sdb1, SDB2 and so on the partition information output together

[Inter-val [Count]]:inter-val is the statistical time interval unit is S,count is the number of statistics

Interpretation of output information:

Basic CPU Output Information:

%user: Percentage of CPU consumed by user processes

%nice: User process priority tuning CPU consumption

%sys: CPU scale consumed by the system core

%iowait: CPU scale consumed by waiting for disk IO

%idle: Percentage of idle CPUs (not including s that wait for disk IO)

Basic Device Output Information:

Device: The name of the appliance

Tps: Number of IO transmissions per second on the device (possibly multiple IO are composed of one IO)

BLK_READ/S: Number of blocks (kernel 2.4, block=512byte) read from device per second

BLK_WRTN/S: Number per second written to device block (kernel 2.4 or more, Block=512byte)

Blk_read: The total number of blocks read from the device during the time interval

BLK_WRTN: The total number of blocks written to the device during the time interval

Note: Activating the-K|-M option will change to kb_* or mb_*

The-x option expands the output information:

RRQM/S: Number of read operations per second for merge (multiple IO merges)

wrqm/s: Number of write operations per second for merge (multiple IO merges)

R/S: Number of Read IO devices completed per second

W/S: Number of Write IO devices completed per second

RSEC/S: Number of Read sectors per second

WSEC/S: Number of Write sectors per second Note: Activation-k|-m will become rkb/s wkb/s | rmb/s wmb/s

Avgrq-sz: Average per IO device size (in sectors) because there is a merge read or write, so each IO size needs to be calculated

Avgqu-sz: Average I/O Queue Length

Await: The wait time for each IO device, including IO service time (milliseconds).

the size of an await typically depends on the service time (SVCTM) and the length of the I/O queue and the emit mode of the I/O request.

Usage examples:

The basic analysis is over, let's take a look at some examples of use. A detailed explanation of the parameters is skipped.