System performance monitoring Tool-Iostat

It is mainly used to monitor the IO load of the system equipment, iostat the statistics from the start of the system startup at the first run, and then run Iostat to display statistics from the last time the command was run. Users can obtain the required statistics by specifying the number and time of the statistics. The main source of Iostat data is/proc/partitions.
-C Displays only CPU rows
-D displays only disk rows
-k displays disk output in kilobytes
-m displays the disk output in units of M.
-T includes timestamps in the output
-X includes extended disk metrics in the output

1) only display the IO load of the device, which refreshes and outputs the result once every 1 seconds, output 3 times after Iostat exit
Iostat-d 1 3
Linux 2.6.32-71.el6.i686 (stephen-pc) 11/16/2011 _i686_ (1 CPU)
Device:tps blk_read/s blk_wrtn/s Blk_read Blk_wrtn
SDA 5.35 258.39 26.19 538210 54560

Device:tps blk_read/s blk_wrtn/s Blk_read Blk_wrtn
SDA 0.00 0.00 0.00 0 0

Device:tps blk_read/s blk_wrtn/s Blk_read Blk_wrtn
SDA 0.00 0.00 0.00 0 0

Device:tps blk_read/s blk_wrtn/s Blk_read Blk_wrtn
SDA 0.00 0.00 0.00 0 0

BLK_READ/S the number of blocks (sectors) Read per second.
BLK_WRTN/S the number of blocks (sectors) written per second.
Blk_read the total number of blocks (sectors) read.
BLK_WRTN number of total blocks (sectors) written.

2) display and IO-related extended data
IOSTAT-DX 1 3

device:rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await SVCTM%util
SDA 5.27 1.31 2.82 1.14 189.49 19.50 52.75 0.53 133.04 10.74 4.26

device:rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await SVCTM%util
SDA 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

device:rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await SVCTM%util
SDA 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

RRQM/S number of Read requests merged per second in the queue
WRQM/S number of write requests consolidated per second in the queue
R/S number of Read requests completed per second
W/S number of write requests completed per second
RSEC/S number of sectors read per second
WSEC/S number of sectors written per second
Avgrq-sz the size of the average request sector
Avgqu-sz the length of the average request queue, the shorter the queue length the better.
Await the average wait time for each request, this time includes the queue time and service time, that is, in general, await is greater than SVCTM, their difference is smaller, then the shorter the queue time, conversely, the greater the difference, the longer the queue time indicates that the system has a problem.

SVCTM The service time (ms) of each device IO operation, the closer to the await note the less waiting time.
utilization of util equipment. All processing IO time in the statistical time, divided by the total statistical time. For example, if the statistic interval is 1 seconds, the device has 0.8 seconds to process Io, and 0.2 seconds is idle, then the device's%util = 0.8/1 = 80%, so this parameter implies the device's busy level. Generally, if this parameter is 100% indicates that the device is already running close to full load (of course if it is a multi-disk, even if%util is 100% because of the concurrency of the disk, disk usage may not be the bottleneck).

System performance monitoring Tool-Iostat