iostat(1M)
NAME
iostat - report I/O statistics
SYNOPSIS
/usr/bin/iostat [-cCdDeEiImMnpPrstxXz] [-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 cumulative
residence-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 this kernel status command, the "state"
of the kernel can change. An example would be CPUs going
online or offline. iostat reports this as one or more of the
following messages:
device_name added
device_name removed
NFS_filesystem mounted
NFS_filesystem unmounted
cpu[s] taken offline: cpuid
cpu[s] brought online: cpuid
where device_name, NFS_filesystem and cpuid are replaced
with the actual name or names of the entities formatted
according to other options.
For more general system statistics, use sar(1), sar(1M), or
vmstat(1M).
OPTIONS
The iostat utility's activity class options default to tdc
(terminal, disk, and CPU). If any activity class options are
specified, the default is completely overridden. Therefore,
if only -d is specified, neither terminal nor CPU statistics
will be reported. The last disk option specified (-d, -D, or
-x) is the only one that is used.
The following options are supported:
-c Report the percentage of time the system has spent in
user mode, in system mode, waiting for I/O, and
idling.
-C When the -n and -x options are also selected, report
extended disk statistics aggregated by controller id.
-d For each disk, report the number of kilobytes
transferred per second, the number of transfers per
second, and the average service time in milliseconds.
-D For each disk, report the reads per second, writes per
second, and percentage disk utilization.
-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 identifier
registered by a driver through ddi_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 unlim-
ited 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.
-M Display data throughput in MB/sec instead of KB/sec.
-n Display names in descriptive format (for example,
cXtYdZ, rmt/N, server:/export/path).
-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 ctime(3C).
-x For each disk, report extended disk statistics. The
output is in tabular form.
-X For disks under scsi_vhci control, also report statis-
tics in the form of target.controller.
-z Do not print lines whose underlying data values are
all zeros.
OPERANDS
The following operands are supported:
disk Explicitly specify the disks to be reported; in addi-
tion to any explicit disks, any active disks up to the
disk limit (see -l above) will also be reported.
count Display only count reports.
interval
Report once each interval seconds.
EXAMPLES
Example 1: Using the iostat command
example% iostat -xtc 5 2
extended device statistics tty cpu
device 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 1 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 cpu
device 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 0
device
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
(queue length)
actv average number of transactions actively being serviced
(removed from the queue but not yet completed)
svc_t average service time, in milliseconds
%w percent of time there are transactions waiting for
service (queue non-empty)
%b percent of time the disk is busy (transactions in pro-
gress)
Example 2: Using the iostat command
example% iostat -xnp
extended device statistics
r/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 expositor:/export/home3/user3
The fields have the same meanings as in the previous exam-
ple, with the following additions:
wsvc_t
average service time in wait queue, in milliseconds
asvc_t
average service time active transactions, in mil-
liseconds
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
SEE ALSO
sar(1), sar(1M), vmstat(1M), time(2), ctime(3C), attri-
butes(5), scsi_vhci(7D)
System Administration Guide: Basic Administration
NOTES
The sum of CPU utilization might vary slightly from 100
because of rounding errors in the production of a percentage
figure.
Man(1) output converted with
man2html