iostat(1M)																iostat(1M)

NAME

       iostat - report I/O statistics

SYNOPSIS

       /usr/bin/iostat [-cCdDeEiImMnpPrstxXz] [-l n] [-T u | d] [disk...] [ interval [count]]

       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,  uti-
       lization,  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 message is included  in  the
       iostat output, in one of the following forms:

       <<device added: sd0>>
       <<device removed: sd0>>
       <<partition added: sd0,a>>
       <<partition removed: sd0,a>>
       <<NFS mounted: nfs1>>
       <<NFS unmounted: nfs1>>
       <<multi-path added: ssd4>>
       <<multi-path removed: ssd4>>
       <<controller added: c1>>
       <<controller removed: c1>>
       <<processors added: 1, 3>>
       <<processors removed: 1, 3>>

       Note that the names printed in these state change messages are affected by the -n and -m options as appropriate.

       For more general system statistics, use sar(1), sar(1M), or vmstat(1M).

   Output
       The 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 second

			       The 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 r/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 serviced (removed from the queue but not yet completed)

			       This is the number of I/O operations accepted, but not yet serviced, by the device.

       svc_t		       average response time of transactions, in milliseconds

			       The  svc_t  output  reports  the overall response time, rather than the service time, of a device. The overall time
			       includes the time that transactions are in queue and the time that transactions are being serviced. The time  spent
			       in queue is 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 shown with the -x option and appears in the asvc_t output  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 milliseconds

       asvc_t		       average service time of active transactions, in milliseconds

       wt		       the I/O wait time is no longer calculated as a percentage of CPU time, and this statistic will always return zero.

       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. See the NOTES
		       section for more information.

       -C	       When the -x option is 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  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 example, 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 more easily associated with physical hardware characteristics.
		       The  cXtYdZsN format is particularly useful in FibreChannel (FC) environments where the FC World Wide Name appears in the t
		       field.

       -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	       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  hard-
		       ware characteristics. Using the cXtYdZsN format is particularly helpful in the FibreChannel environments where the FC World
		       Wide Name appears in the t field.

       -X	       For disks under scsi_vhci control, also report statistics in the form of target.controller.

       -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 identifying problems.

       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 disks up to the disk limit  (see
		       -l above) will also be reported.

       interval        Report once each interval seconds.

       Example 1: Using iostat to Generate User and System Operation Statistics

       The following command displays two reports of extended device statistics, aggregated by controller id, for user (us) and system (sy) opera-
       tions. 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 20
			   extended device statistics
	 r/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 statistics
	 r/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	d10

       Example 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 -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  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	       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

       Example 3: Using iostat to Generate Partition and Device Statistics

       The  following command generates partition and device statistics for each disk. Because the -n option is used with the -x option, disks are
       identified by controller names.

       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 fuji:/export/home3/user3

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |See below.		   |
       +-----------------------------+-----------------------------+

       Invocation is evolving. Human readable output is unstable.

       sar(1), sar(1M), mpstat(1M), vmstat(1M), time(2), ctime(3C), attributes(5), scsi_vhci(7D)

       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 statistics. 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 processors in the processor
       set of the pool to which the zone is bound.

								    29 Jun 2005 							iostat(1M)