Article from: https://www.cnblogs.com/ghj1976/p/5691857.html
Linux system iostat is an abbreviation I / O statistics (input / output statistics), iostat disk operating system will be the active tool is monitored.
It features disk activity statistics reporting the situation, while also reporting the CPU usage. As with vmstat, iostat also has a weakness, is that it can not be the whole situation in-depth analysis, the system only to a process for analysis. iostat belong sysstat package. Can be directly installed with yum install sysstat.
Format:
the iostat [parameters] [Time] [times]
Command parameters:
- Display CPU usage -C
- -d Displays disk usage
- -k in KB display
- display unit to M -m
- -N display disk array (LVM) information
- -n Display NFS usage
- -p [disk] display case disks and partitions
- -t terminal display and CPU
- -x Show Details
- -V Display version information
iostat command
The figure is displayed once every 10 seconds, it has been displayed.
CPU property values
- % User: CPU the percentage of time the user mode.
- % Nice: CPU the percentage of time the user mode with NICE value.
- % System: CPU the percentage of time the system mode.
- % Iowait: CPU waits for input and output completion percentage.
- % Steal: the management of the program to maintain another virtual processor, a virtual CPU waits for the percentage of time unconscious.
- % Idle: the percentage of CPU idle time.
Remarks:
- If the value of% iowait too high, indicates the presence of the hard disk I / O bottleneck,
- % Idle higher value indicates more CPU is idle,
- % Idle value is high if the system slow to respond, it is possible to wait for the CPU to allocate memory, should increase the memory capacity.
- % Idle Sustained value if less than 10, then the relatively low CPU processing capacity of the system, indicating that the system resources need to be resolved is the most CPU.
Disk meaning of each column is as follows:
- rrqm / s: the number of read operations performed per second merge. I.e. rmerge / s
- Merge number of write operations performed per second: wrqm / s. I.e. wmerge / s
- r / s: second reading completion of I / O devices. I.e. rio / s
- w / s: per second write completion of I / O devices. I.e. wio / s
- rsec / s: the number of sectors per read. I.e. rsect / s
- wsec / s: the number of sectors per second write. I.e. wsect / s
- rkB / s: the number of K bytes read per second. Is half rsect / s, because the sector size is 512 bytes
- wkB / s: K bytes per second write. Half wsect / s of
- avgrq-sz: Average per-device I / O operation of the data size (sector)
- avgqu-sz: average I / O queue length.
- await: Average waiting time per device I / O operations (in milliseconds)
- svctm: average service time per device I / O operations (in milliseconds)
- % Util: one second how many percent of the time for I / O operations, or how much time is one second I / O queue is not empty.
Remarks:
- If% util close to 100%, indicating that the generated I / O requests too, I / O system has been at full capacity, the disk may be a bottleneck.
- If svctm close await, for I / O almost no wait time;
- If the svctm await much larger than, for I / O queue is too long, too slow IO response, the need for optimization necessary.
- If avgqu-sz relatively large, expressed in equivalents waiting io