iostat

说明

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.

输出列说明

列名	说明
tps	每秒的事务，称为 IOPS
kB_read/s	每秒读取的千字节数
kB_wrtn/s	每秒写入的千字节数
kB_read	读取的总千字节数
kB_wrtn	写入的总千字节数

实例演示

# 用 -yz 可以忽略干扰实时监控
iostat -yz 1 3

使用示例

iostat

# 查看指定磁盘 sda
iostat sda

# 使用 MB 为单位进行显示
iostat sda -m

# 持续显示，间隔 1s
iostat -d sda 1

# 1s 间隔，连续显示 5 次
iostat -d sda 1 5

# 显示 sda 设备的分区，1s 间隔，连续显示 5 次
iostat -d -p sda 1 5

# -N Display the registered device mapper names for any device mapper devices.
# Useful for viewing LVM2 statistics.
iostat -N

# -x 显示更详细的信息，1s 间隔，连续显示 5 次 
iostat -x -d sda 1 5

# # 1s 间隔，连续显示 5 次 
iostat -d sda 1 5

# 查看 CPU 状态
iostat -c

不加 -N 和加 -N 结果对比

iostat
Linux 5.14.0-362.8.1.el9_3.x86_64 (rocky1)      07/19/2024      _x86_64_        (2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.12    0.01    0.20    0.00    0.00   99.67

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
dm-0              0.54         0.93        16.99         0.00     893895   16288840          0
dm-1              0.00         0.00         0.00         0.00       2216        220          0
dm-2              0.00         0.00         0.00         0.00       1140       2048          0
sda               0.50         1.00        16.99         0.00     956441   16293177          0
sr0               0.00         0.00         0.00         0.00       2096          0          0

iostat -N
Linux 5.14.0-362.8.1.el9_3.x86_64 (rocky1)      07/19/2024      _x86_64_        (2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.12    0.01    0.20    0.00    0.00   99.67

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
rl_miwifi--rb06--srv-root     0.54         0.93        16.99         0.00     893895   16288840          0
rl_miwifi--rb06--srv-swap     0.00         0.00         0.00         0.00       2216        220          0
rl_miwifi--rb06--srv-home     0.00         0.00         0.00         0.00       1140       2048          0
sda               0.50         1.00        16.99         0.00     956441   16293177          0
sr0               0.00         0.00         0.00         0.00       2096          0          0

-x 选项输出结果说明

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.

-x 输出结果

iostat -x -d sda 1 5
Linux 5.14.0-362.8.1.el9_3.x86_64 (rocky1)      07/19/2024      _x86_64_        (2 CPU)

Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.03      1.00     0.00   4.69    0.44    39.53    0.47     17.01     0.06  11.01    2.72    36.07    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.03


Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00


Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00


Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00


Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda              0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00      0.00     0.00   0.00    0.00     0.00    0.00    0.00    0.00   0.00

实验：判断是大 IO 还是小 IO

模拟磁盘写入

dd if=/dev/zero of=/tmp/test.1 bs=8k count=102400 oflag=direct

iostat 监控

iostat -d sda 1 100

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda           13762.00         0.00    110096.00         0.00          0     110096          0


Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda           13672.00         0.00    109376.00         0.00          0     109376          0


Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda           13710.00         0.00    109680.00         0.00          0     109680          0


Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda            8460.00         0.00     67680.00         0.00          0      67680          0


Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda               0.00         0.00         0.00         0.00          0          0          0


Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda               0.00         0.00         0.00         0.00          0          0          0

计算 IO 大小

# (kB_read/s + kB_wrtn/s) / tps
# 选两组数据
bc
109680/13710
8
109680/13710
8

由计算结果可得出 IO 大小为 8K