iostat [-CUdKIoT?] [-c count] [-n devs] [-w wait] [drives]

displays kernel I/O statistics on terminal, device and cpu operations.

The first statistics that are printed are averaged over the system uptime.

-c count   Repeat count times.
-w seconds wait seconds between each display. default 1.
-C CPU statistics. default on, -d supresses.
-U system load averages. default on, -d supresses.
-T BSD TTY statistics. default, unless -d is specified.
-d only device statistics. (i.e. supress -C -U)
-I total for period, rather than
average per second
-n n up to n of devices.
-o old-style i.e. Sectors/second, transfers/second, and miliseconds/seek .
-I total blocks/sectors, total transfers, and miliseconds per seek.
-K block count in kilobytes rather then the block size.
tty tin   characters read from terminals
tout characters written to terminals
devices Device operations.
KB/t    KiloBytes per transfer
tps     Transfers per second
MB/s    MegaBytes per second 
-I shows:
KB/t    KiloBytes per transfer
xfrs    total number of transfers
MB      total number of megabytes transferred 
old-style -o shows:
sps     sectors transferred per second
tps     Transfers Per Second
msps    average MilliSeconds Per transaction
old-style with -o -I shows:
blk     total Blocks/sectors transferred 
xfr     total transfers
msps    average MilliSeconds Per transaction

cpu us      % of cpu time in user mode;  
sy      system mode; id    idle mode


Display statistics for the first disk device every second ad infinitum.
/usr/sbin/iostat -w 1 disk0

     KB/t tps  MB/s 
     5.04   75  0.37
     0.00    0  0.00
     8.00    4  0.03
    13.56   16  0.21
     4.39  433  1.85
     4.01 4074 15.95
     4.00 4156 16.25
     4.01 3907 15.29
     4.09 1681  6.71

(This part can be supressed by using -d)
 cpu        load average       comments by Ed
us sy id   1m  5m    15m 
 4  2 89  0.12  0.33  0.38  <-average 
 4  3 92  0.12  0.33  0.38  < quite 
 4  3 92  0.11  0.32  0.38  < quite 
 2  2 96  0.10  0.31  0.37 <  Disk I/O starting 
46  4 91  0.10  0.31  0.37 <    continues; user 91 jumps the CPU
19  3 79  0.10  0.31  0.37   continues 
21  1 78  0.10  0.31  0.37   continues 
18  3 80  0.10  0.31  0.37 
10  2 59  0.17  0.33  0.38 < CPU time picks up too 
for the devices 8 times, one second interval(default). First display is average to date.
/usr/sbin/iostat -c 8

total statistics every three seconds ad infinitum.

/usr/sbin/iostat -Iw 3

total statistics using the old-style 9 times, with a 2 second wait between each measurement/display. The -d flag generally disables the TTY and CPU displays, but since the -T and -C flags are given, the TTY and CPU displays will be displayed.

/usr/sbin/iostat -odICTw 2 -c 9

see: fstat(1), netstat(1), nfsstat(1), ps(1), pstat(8)

The sections starting with Interpreting system activity in Installing and Operating 4.3BSD.

 /usr/bin/iostat [ options... ] [  [  ] ]

[ -c | -d ] 
[ -k | -m ]  KB or MB
[ -t ] add time of day to report
[ -V ] [ -x ] [ -n ] [ -h ] [ -N ]
                 [  [ ... ] | ALL ] [ -p [  | ALL ] ]

Linux 2.6.18-128.1.6.el5PAE (   05/20/10

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           5.55    0.43    2.68    3.94    0.00   87.40

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda              66.56        75.89        41.82 1694565361  933863720
sda1              0.00         0.03         0.00     763240        232
sda2             66.56        75.82        41.82 1693102450  933829400
sda3              0.00         0.00         0.00      14263      34088
sdb              30.42        28.25        50.68  630909740 1131662488
sdb1             30.42        28.24        50.68  630674556 1131662488


system activity reporter

sar [-dgpu] [-n mode] [-o filename] t [n]
sar [-dgpu] [-n mode] [-e time] [-f filename] [-i seconds] [-s time]

cumulative statistic counters maintained by the operating system. n samples are reported at t second intervals. -o write binary sampling data to filename.

Sampling input comes from a previously recorded, binary activity file, specified using -f filename WIthout -f default /var/log/sa/sadd, where dd the day of the month.

The starting and ending time of the report can be restricted using the -e and -s options. Here, the time field is specified in the form hh[:mm[:ss]]. Finally, the -i option can be used to select the sampling interval. Only records at least seconds apart will be reported. When the -i option is not used, all of the previously recorded interval samples are reported. Due to the nature of on-going sample collection, the data is reported in a verbose mode when more than one sampling option is specified. Column headers are printed at the beginning of the report; averages are printed when the sar command terminates.

     The following options restrict the sample set that sar reports.

     -d       Report disk activity.  
              device   The BSD name of the device.  
              r+w/s    The number of reads and writes per second.  
              blks/s   Number of blocks (in device's default blocksize) transferred to a device per second.

     -g       Report page-out activity.  
              pgout/s  The number of pages paged out per second.

     -p       Report page-in and page fault activity 
              pgin/s   The number of pages paged in per second.  
              pflts/s  The number of faults that caused a page to be copied in per second.  
              vflts/s  The number of times vm_fault routine has been called.

     -n mode  Report network activity with modes DEV, EDEV, or PPP.  Multiple network modes can be specified.

              DEV      The DEV mode reports network device statistics.  The following information is displayed for each interface.

                       IFACE     The network interface name.  
                       Ipkts/s   The number of packets received per second.  
                       Ibytes/s  The number of bytes received per second.  
                       Opkts/s   The number of packets sent per second.  
                       Obytes/s  The number of bytes sent per second.

              EDEV     The EDEV mode reports network device error statistics. The following information is displayed for each

                       IFACE    The interface name.  
                       Ierrs/s  The input errors per second.  
                       Oerrs/s  The output errors per second.  
                       Coll/s   The collisions that occurred per second.  
                       Drops/s  The number of dropped packets per second.

              PPP      The PPP mode must be specified in order to display ppp connections in the network statistics. This will
                       also turn on the PPP modify mode in sadc (8) when sampling data is not being read from a file.  By
                       default, both the collection and reporting of ppp statistics is turned off.  See sadc (8).

     -u       Report CPU activity (default)

              %usr, %sys, and %idle

              These report the percentage of time running in user mode, system mode and idle.

     /var/log/sa/sadd  Default daily activity file that holds the binary sampling data.  dd are digits that represent the day
                       of the month.

     fs_usage(1), netstat(1), sc_usage(1), top(1), vm_stat(1), iostat(8), sa1(8), sa2(8), sadc(8)

 > sudo sar -d 5 30

20:40:57   device    r+w/s    blks/s
New Disk: [disk0] IODeviceTree:/PCI0@0/SATA@B/PRT0@0/PMP@0/@0:0
20:41:02   disk0        1          9
20:41:07   disk0        8        458
20:41:12   disk0        8        361
20:41:17   disk0       13        332
20:41:22   disk0        0          6
20:41:27   disk0        0          6
20:41:32   disk0        1          9
Average:                 4        80