System Administration Commands iostat(1M)
NAME
iostat - report I/O statistics
SYNOPSIS
/usr/bin/iostat [-cCdDeEiImMnpPrstxXYz] [-l n] [-T u | d]
[disk]... [interval [count]]DESCRIPTION
The iostat utility iteratively reports terminal, disk, and
tape I/O activity, as well as CPU utilization. The first line of output is for all time since boot; each subsequent line is for the prior interval only. To compute this information, the kernel maintains a number of counters. For each disk, the kernel counts reads, writes,
bytes read, and bytes written. The kernel also takes hi-res
time stamps at queue entry and exit points, which allows it to keep track of the residence time and cumulativeresidence-length product for each queue. Using these values,
iostat produces highly accurate measures of throughput,
utilization, queue lengths, transaction rates and service time. For terminals collectively, the kernel simply counts the number of input and output characters. During execution of the kernel status command, the state of the system can change. If relevant, a state change messageis included in the iostat output, in one of the following
forms: <> < > < > < > < > < > <
> <
<> > < > < > < > Note that the names printed in these state change messages are affected by the -n and -m options as appropriate.
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System Administration Commands iostat(1M)
For more general system statistics, use sar(1), sar(1M), or vmstat(1M). OutputThe output of the iostat utility includes the following
information. device name of the disk r/s reads per second w/s writes per second kr/s kilobytes read per secondThe average I/O size during the interval can be computed from kr/s divided by r/s. kw/s kilobytes written per second
The average I/O size during the interval can be computed from kw/s divided by w/s. wait average number of transactions waiting for service (queue length)
This is the number of I/O operations held in the device driver queue waiting for acceptance by the device.
actv average number of transactions actively being ser-
viced (removed from the queue but not yet com-
pleted)This is the number of I/O operations accepted, but not yet serviced, by the device.
svc_t average response time of transactions, in mil-
lisecondsThe svc_t output reports the overall response
time, rather than the service time, of a device.The overall time includes the time that transac-
tions are in queue and the time that transactions are being serviced. The time spent in queue isSunOS 5.11 Last change: 23 Mar 2009 2
System Administration Commands iostat(1M)
shown with the -x option in the wsvc_t output
column. The time spent servicing transactions is the true service time. Service time is also shownwith the -x option and appears in the asvc_t out-
put column of the same report.%w percent of time there are transactions waiting for
service (queue non-empty)
%b percent of time the disk is busy (transactions in
progress)wsvc_t average service time in wait queue, in mil-
lisecondsasvc_t average service time of active transactions, in
millisecondswt the I/O wait time is no longer calculated as a percentage of CPU time, and this statistic will always return zero. OPTIONS The following options are supported:
-c Report the percentage of time the system has
spent in user mode, in system mode, waiting forI/O, and idling. See the NOTES section for more information.
-C When the -x option is also selected, report
extended disk statistics aggregated by con-
troller id.-d For each disk, report the number of kilobytes
transferred per second, the number of transfersper second, and the average service time in mil-
liseconds.-D For each disk, report the reads per second,
writes per second, and percentage disk utiliza-
tion.SunOS 5.11 Last change: 23 Mar 2009 3
System Administration Commands iostat(1M)
-e Display device error summary statistics. The
total errors, hard errors, soft errors, and transport errors are displayed.-E Display all device error statistics.
-i In -E output, display the Device ID instead of
the Serial No. The Device Id is a unique iden-
tifier registered by a driver throughddi_devid_register(9F).
-I Report the counts in each interval, rather than
rates (where applicable).-l n Limit the number of disks included in the report
to n; the disk limit defaults to 4 for -d and
-D, and unlimited for -x. Note: disks explicitly
requested (see disk below) are not subject to this disk limit.-m Report file system mount points. This option is
most useful if the -P or -p option is also
specified or used in conjunction with -Xn or
-en. The -m option is useful only if the mount
point is actually listed in the output. This option can only be used in conjunction with the-n option.
-M Display data throughput in MB/sec instead of
KB/sec.-n Display names in descriptive format. For exam-
ple, cXtYdZ, rmt/N, server:/export/path. By default, disks are identified by instance
names such as ssd23 or md301. Combining the -n
option with the -x option causes disk names to
display in the cXtYdZsN format which is moreeasily associated with physical hardware charac-
teristics. The cXtYdZsN format is particularly useful in FibreChannel (FC) environments where the FC World Wide Name appears in the t field.SunOS 5.11 Last change: 23 Mar 2009 4
System Administration Commands iostat(1M)
-p For each disk, report per-partition statistics
in addition to per-device statistics.
-P For each disk, report per-partition statistics
only, no per-device statistics.
-r Display data in a comma-separated format.
-s Suppress messages related to state changes.
-t Report the number of characters read and written
to terminals per second.-T u | d Display a time stamp.
Specify u for a printed representation of the internal representation of time. See time(2). Specify d for standard date format. See date(1).-X For disks under scsi_vhci(7D) control, in addi-
tion to disk lun statistics, also report statis-
tics for lun.controller.-x Report extended disk statistics. By default,
disks are identified by instance names such as ssd23 or md301. Combining the x option with the-n option causes disk names to display in the
cXtYdZsN format, more easily associated with physical hardware characteristics. Using the cXtYdZsN format is particularly helpful in the FibreChannel environments where the FC World Wide Name appears in the t field.If no output display is requested (no -x, -e,
-E), -x is implied.
-Y For disks under scsi_vhci(7D) control, in addi-
tion to disk lun statistics, also report statis-
tics for lun.targetport and lun.targetport.controller.In -n (descriptive) mode the targetport is shown
in using the target-port property of the path.
Without -n the targetport is shown using the
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System Administration Commands iostat(1M)
shorter port-id. All target ports with the same
target-port property value share the same port-
id. The target-port-to-port-id association does
not persist across reboot.If no output display is requested (no -x, -e,
-E), -x is implied.
-z Do not print lines whose underlying data values
are all zeros.The option set -xcnCXTdz interval is particularly useful for
determining whether disk I/O problems exist and for identi-
fying problems. OPERANDS The following operands are supported: count Display only count reports. disk Explicitly specify the disks to be reported; in addition to any explicit disks, any active disksup to the disk limit (see -l above) will also be
reported. interval Report once each interval seconds.EXAMPLES
Example 1 Using iostat to Generate User and System Operation
StatisticsThe following command displays two reports of extended dev-
ice statistics, aggregated by controller id, for user (us)and system (sy) operations. Because the -n option is used
with the -x option, devices are identified by controller
names.example% iostat -xcnCXTdz 5
Mon Nov 24 14:58:36 2003 cpu us sy wt id 14 31 0 20SunOS 5.11 Last change: 23 Mar 2009 6
System Administration Commands iostat(1M)
extended device statisticsr/s w/s kr/s kw wait actv wsvc_t asvc_t %w %b device
3.8 29.9 145.8 44.0 0.0 0.2 0.1 6.4 0 5 c0 666.3 814.8 12577.6 17591.1 91.3 82.3 61.6 55.6 0 2 c12 180.0 234.6 4401.1 5712.6 0.0 147.7 0.0 356.3 0 98 d10 Mon Nov 24 14:58:41 2003 cpu us sy wt id 11 31 0 22 extended device statisticsr/s w/s kr/s kw wait actv wsvc_t asvc_t %w %b device
0.8 41.0 5.2 20.5 0.0 0.2 0.2 4.4 0 6 c0 565.3 581.7 8573.2 10458.9 0.0 26.6 0.0 23.2 0 3 c12 106.5 81.3 3393.2 1948.6 0.0 5.7 0.0 30.1 0 99 d10Example 2 Using iostat to Generate TTY Statistics
The following command displays two reports on the activity of five disks in different modes of operation. Because the-x option is used, disks are identified by instance names.
example% iostat -x tc 5 2
extended device statistics tty cpudevice r/s w/s kr/s kw/s wait actv svc_t %w %b tin tout us sy wt id
sd0 0.4 0.3 10.4 8.0 0.0 0.0 36.9 0 1 0 10 0 0 0 99 sd1 0.0 0.0 0.3 0.4 0.0 0.0 35.0 0 0 sd6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 nfs1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 nfs2 0.0 0.0 0.0 0.1 0.0 0.0 35.6 0 0 extended device statistics tty cpudevice r/s w/s kr/s kw/s wait actv svc_t %w %b tin tout us sy wt id
sd0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 0 155 0 0 0 100 sd1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 sd6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 nfs1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 nfs2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0Example 3 Using iostat to Generate Partition and Device
StatisticsSunOS 5.11 Last change: 23 Mar 2009 7
System Administration Commands iostat(1M)
The following command generates partition and device statis-
tics for each disk. Because the -n option is used with the
-x option, disks are identified by controller names.
example% iostat -xnp
extended device statisticsr/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.4 0.3 10.4 7.9 0.0 0.0 0.0 36.9 0 1 c0t0d0 0.3 0.3 9.0 7.3 0.0 0.0 0.0 37.2 0 1 c0t0d0s0 0.0 0.0 0.1 0.5 0.0 0.0 0.0 34.0 0 0 c0t0d0s1 0.0 0.0 0.0 0.1 0.0 0.0 0.6 35.0 0 0 fuji:/export/home/user3 Example 4 Show Translation from Instance Name to Descriptive NameThe following example illustrates the use of iostat to
translate a specific instance name to a descriptive name.example% iostat -xn sd1
extended device statisticsr/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c8t1d0 Example 5 Show Target Port and Controller Activity for a Specific Disk In the following example, there are four controllers, all connected to the same target port.# iostat -Y ssd22
extended device statisticsdevice r/s w/s kr/s kw/s wait actv svc_t %w %b
ssd22 0.2 0.0 1.5 0.0 0.0 0.0 0.7 0 0 ssd22.t2 0.2 0.0 1.5 0.0 0.0 0.0 0.0 0 0 ssd22.t2.fp0 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0 0 ssd22.t2.fp1 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0 0 ssd22.t2.fp2 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0 0 ssd22.t2.fp3 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0 0SunOS 5.11 Last change: 23 Mar 2009 8
System Administration Commands iostat(1M)
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcs ||_____________________________|_____________________________|
| Interface Stability | See below. ||_____________________________|_____________________________|
Invocation is evolving. Human readable output is unstable.SEE ALSO
date(1), sar(1), sar(1M), mpstat(1M), vmstat(1M), time(2),attributes(5), scsi_vhci(7D)
NOTES The sum of CPU utilization might vary slightly from 100 because of rounding errors in the production of a percentage figure.The svc_t response time is not particularly significant when
the I/0 (r/s+w/s) rates are under 0.5 per second. Harmless spikes are fairly normal in such cases.The mpstat utility reports the same wt, usr, and sys statis-
tics. See mpstat(1M) for more information. When executed in a zone and if the pools facility is active,iostat(1M) will only provide information for those proces-
sors in the processor set of the pool to which the zone is bound.SunOS 5.11 Last change: 23 Mar 2009 9