vmstat的應用詳解

Solaris Performance Monitoring & Tuning - iostat , vmstat & netstat

Introduction to iostat , vmstat and netstat

This document is primarily written with reference to solaris performance monitoring and tuning but these tools are available in other unix variants also with slight syntax difference.

iostat , vmstat and netstat are three most commonly used tools for performance monitoring . These comes built in with the operating system and are easy to use .iostat stands for input output statistics and reports statistics for i/o devices such as disk drives . vmstat gives the statistics for virtual Memory and netstat gives the network statstics .

Following paragraphs describes these tools and their usage for performance monitoring and if you need more information there are some very good solaris performance monitoring books available at .

Table of content :

1. Iostat

• Syntax
• example
• Result and Solutions

2. vmstat

• syntax
• example
• Result and Solutions

3. netstat

• syntax
• example
• Result and Solutions

4. Next Steps

iostat reports terminal and disk I/O activity and CPU utilization. The first line of output is for the time period since boot & each subsequent line is for the prior interval . Kernel maintains a number of counters to keep track of the values.

iostat's activity class options default to tdc (terminal, disk, and CPU). If any other option/s are specified, this default is completely overridden i.e. iostat -d will report only statistics about the disks.

Basic synctax is iostat interval count

option - let you specify the device for which information is needed like disk , cpu or terminal. (-d , -c , -t or -tdc ) . x options gives the extended statistics .

interval - is time period in seconds between two samples . iostat 4 will give data at each 4 seconds interval.

count - is the number of times the data is needed . iostat 4 5 will give data at 4 seconds interval 5 times

--&gt

 $ iostat -xtc 5 2
                          extended disk statistics       tty         cpu
     disk r/s  w/s Kr/s Kw/s wait actv svc_t  %w  %b  tin tout us sy wt id
     sd0   2.6 3.0 20.7 22.7 0.1  0.2  59.2   6   19   0   84  3  85 11 0
     sd1   4.2 1.0 33.5  8.0 0.0  0.2  47.2   2   23
     sd2   0.0 0.0  0.0  0.0 0.0  0.0   0.0   0    0
     sd3  10.2 1.6 51.4 12.8 0.1  0.3  31.2   3   31
 

     The fields have the following meanings:

      disk    name of the disk
      r/s     reads per second
      w/s     writes per second
      Kr/s    kilobytes read per second
      Kw/s    kilobytes written per second
      wait    average number of transactions waiting for service (Q length)

      actv    average number of transactions  actively  

              being serviced (removed  from  the

 	      queue but not yet
              completed)
      %w      percent of time there are transactions  waiting
              for service (queue non-empty)
      %b      percent of time the disk is busy  (transactions
                  in progress)