The iostat command, when executed with any arguments, displays both the CPU and disk I/O utilization metrics.
选项说明
选项
说明
-c
displays the CPU utilization report
-d
displays the disk I/O utilization report
-y
omits the first report with statistics since system boot
-z
omits any devices for which there is no activity
-x
displays extra columns
The -x option displays extra columns, which include IOPS, as well as throughput metrics for performance characterization and latency analysis. Some the metrics displayed by the -x option are: average read and write request size, average I/O response time, and percentage of time the disk spent in processing I/O request.
Device:
This column gives the device (or partition) name as listed in the /dev directory.
tps Indicate the number of transfers per second that were issued to the device. A transfer is an I/O request to the de‐
vice. Multiple logical requests can be combined into a single I/O request to the device. A transfer is of indetermi‐
nate size.
Blk_read/s (kB_read/s, MB_read/s)
Indicate the amount of data read from the device expressed in a number of blocks (kilobytes, megabytes) per second.
Blocks are equivalent to sectors and therefore have a size of 512 bytes.
Blk_wrtn/s (kB_wrtn/s, MB_wrtn/s)
Indicate the amount of data written to the device expressed in a number of blocks (kilobytes, megabytes) per second.
Blk_dscd/s (kB_dscd/s, MB_dscd/s)
Indicate the amount of data discarded for the device expressed in a number of blocks (kilobytes, megabytes) per sec‐
ond.
Blk_w+d/s (kB_w+d/s, MB_w+d/s)
Indicate the amount of data written to or discarded for the device expressed in a number of blocks (kilobytes,
megabytes) per second.
Blk_read (kB_read, MB_read)
The total number of blocks (kilobytes, megabytes) read.
Blk_wrtn (kB_wrtn, MB_wrtn)
The total number of blocks (kilobytes, megabytes) written.
Blk_dscd (kB_dscd, MB_dscd)
The total number of blocks (kilobytes, megabytes) discarded.
Blk_w+d (kB_w+d, MB_w+d)
The total number of blocks (kilobytes, megabytes) written or discarded.
r/s The number (after merges) of read requests completed per second for the device.
w/s The number (after merges) of write requests completed per second for the device.
d/s The number (after merges) of discard requests completed per second for the device.
f/s The number (after merges) of flush requests completed per second for the device. This counts flush requests executed
by disks. Flush requests are not tracked for partitions. Before being merged, flush operations are counted as
writes.
sec/s (kB/s, MB/s)
The number of sectors (kilobytes, megabytes) read from, written to or discarded for the device per second.
rsec/s (rkB/s, rMB/s)
The number of sectors (kilobytes, megabytes) read from the device per second.
wsec/s (wkB/s, wMB/s)
The number of sectors (kilobytes, megabytes) written to the device per second.
dsec/s (dkB/s, dMB/s)
The number of sectors (kilobytes, megabytes) discarded for the device per second.
rqm/s The number of I/O requests merged per second that were queued to the device.
rrqm/s The number of read requests merged per second that were queued to the device.
wrqm/s The number of write requests merged per second that were queued to the device.
drqm/s The number of discard requests merged per second that were queued to the device.
%rrqm The percentage of read requests merged together before being sent to the device.
%wrqm The percentage of write requests merged together before being sent to the device.
%drqm The percentage of discard requests merged together before being sent to the device.
areq-sz
The average size (in kilobytes) of the I/O requests that were issued to the device.
Note: In previous versions, this field was known as avgrq-sz and was expressed in sectors.
rareq-sz
The average size (in kilobytes) of the read requests that were issued to the device.
wareq-sz
The average size (in kilobytes) of the write requests that were issued to the device.
dareq-sz
The average size (in kilobytes) of the discard requests that were issued to the device.
await The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent
by the requests in queue and the time spent servicing them.
r_await
The average time (in milliseconds) for read requests issued to the device to be served. This includes the time spent
by the requests in queue and the time spent servicing them.
w_await
The average time (in milliseconds) for write requests issued to the device to be served. This includes the time spent
by the requests in queue and the time spent servicing them.
d_await
The average time (in milliseconds) for discard requests issued to the device to be served. This includes the time
spent by the requests in queue and the time spent servicing them.
f_await
The average time (in milliseconds) for flush requests issued to the device to be served. The block layer combines
flush requests and executes at most one at a time. Thus flush operations could be twice as long: Wait for current
flush request, then execute it, then wait for the next one.
aqu-sz The average queue length of the requests that were issued to the device.
Note: In previous versions, this field was known as avgqu-sz.
%util Percentage of elapsed time during which I/O requests were issued to the device (bandwidth utilization for the de‐
vice). Device saturation occurs when this value is close to 100% for devices serving requests serially. But for de‐
vices serving requests in parallel, such as RAID arrays and modern SSDs, this number does not reflect their perfor‐
mance limits.
