From : The home of the scriptLinux View disk IO status Operations
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Linux system has a performance problem, generally we can use Top.iostat,vmstat and other commands to view the initial location problem. Which Iostat can provide us with rich IO status Data Linux system has a performance problem, generally we can through the Top.iostat,vmstat and other commands to view the initial positioning problems. Iostat can provide us with rich IO status data. Www.jb51.net
Iostat Results Analysis
[Email protected] linux]$ Iostat-x-K
Linux 2.6.18-128.el5_cyou_1.0 (SZ-8.30) 09/08/2011
AVG-CPU:%user%nice%system%iowait%steal%idle
16.58 0.00 2.79 0.46 0.00 80.16
device:rrqm/s wrqm/s r/s w/s rkb/s wkb/s avgrq-sz avgqu-sz await SVCTM%util
SDA 0.06 29.28 0.22 37.14 10.21 265.68 14.77 0.02 0.51 0.15 0.55
SDA1 0.00 0.00 0.00 0.00 0.00 0.00 10.79 0.00 2.66 2.43 0.00
Sda2 0.01 0.78 0.10 0.36 0.81 4.58 23.51 0.00 1.21 0.84 0.04
Sda3 0.03 15.17 0.09 35.39 8.98 202.24 11.91 0.01 0.26 0.12 0.44
SDA4 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 33.33 33.33 0.00
Sda5 0.01 1.59 0.03 0.51 0.34 8.40 32.20 0.00 1.19 0.58 0.03
Sda6 0.00 0.00 0.00 0.12 0.00 0.48 8.18 0.00 5.02 4.53 0.05
SDA7 0.00 0.00 0.00 0.00 0.00 0.00 45.00 0.00 5.52 3.04 0.00
SDA8 0.00 0.00 0.00 0.00 0.00 0.00 40.88 0.00 7.62 6.03 0.00
SDA9 0.00 0.00 0.00 0.00 0.00 0.00 39.71 0.00 7.37 5.83 0.00
SDA10 0.00 0.00 0.00 0.00 0.00 0.00 37.57 0.00 5.70 3.54 0.00
SDA11 0.00 11.74 0.01 0.76 0.08 49.97 131.48 0.01 10.74 0.57 0.04
SDB 0.01 3.91 20.24 20.21 1262.95 1853.94 154.09 0.52 12.84 1.97 7.95
RRQM/S: The number of read operations per second for the merge. Delta (rmerge)/s
WRQM/S: The number of write operations per second for the merge. Delta (wmerge)/s
R/S: Number of Read I/O devices completed per second. Delta (RIO)/s
W/S: Number of write i/0 devices completed per second. Delta (WIO)/s
RSEC/S: Number of Read sectors per second. Delta (rsect)/s
WSEC/S: Number of Write sectors per second. Delta (wsect)/s
rkb/s: Reads K bytes per second. is half the rsec/s because the size of each sector is 512 bytes
wkb/s: Writes K bytes per second. It's half the wsec/s.
Avgrq-sz: The average data size (sector) per device I/O operation. Delta (rsect+wsect)/delta (Rio+wio)
Avgqu-sz: Average I/O queue length. Delta (AVEQ)/s/1000 (because the Aveq unit is milliseconds)
Await: The average wait time (in milliseconds) for each device I/O operation. Delta (ruse+wuse)/delta (Rio+wio)
SVCTM: The average service time (in milliseconds) per device I/O operation. Delta (use)/delta (RIO+WIO)
%util: How much time in a second is spent on I/O operations, or how many times in a second I/O queues are non-empty. Delta (USR)/s/1000 (because the use unit is in milliseconds)
If%util is close to 100%, it indicates that there are too many I/O requests and that the I/O system is fully loaded and that the disk may have bottlenecks.
Comparison of important parameters
%util: How much time is spent in a second for I/O operations, or how many times in a second I/O queues are non-empty
SVCTM: Average service time Per device I/O operation
Await: Average wait time per device I/O operation
Avgqu-sz: Average I/O Queue Length
If the%util is close to 100%, indicating that I/O requests too much, I/O system is full load, the disk may have a bottleneck, the general%util greater than 70%,i/o pressure is relatively large, reading speed has more wait.
You can also combine vmstat to see the b parameter (the number of processes waiting on the resource) and the WA parameter (percentage of CPU time that the I/O wait consumes, high I/O pressure when it is over 30%)
The size of an await typically depends on the service time (SVCTM) and the length of the I/O queue and the emit mode of the I/O request. If the SVCTM is closer to await, it indicates that I/O has little waiting time;
The await is much larger than SVCTM, which indicates that the I/O queue is too long and the application gets slower response times.
Metaphor of the image
r/s+w/s similar to the total number of people who have been
Average Queue Length (AVGQU-SZ) is similar to the average number of people queuing in a unit of time
Average service time (AVCTM) is similar to the cashier's payment speed
Average wait time (await) is similar to the average wait time per person
Average I/O data (AVGRQ-SZ) is similar to what the average person buys
I/O operation rate (%util) is similar to the time scale at which a person is queued at the cashier
SVCTM generally less than await (because the waiting time for waiting requests is repeatedly computed), the size of SVCTM is generally related to disk performance, cpu/memory load will have an impact on it, too many requests will
Indirectly leads to an increase in SVCTM. The size of an await typically depends on the service time (SVCTM) and the length of the I/O queue and the emit mode of the I/O request. If SVCTM is closer to await, I/O has little
Wait time, if the await is much larger than SVCTM, the I/O queue is too long, the response time of the application gets slower, and if the response time is more than the user can tolerate, you can consider replacing the faster disk,
Integer kernel elevator algorithm, optimize application, or upgrade CPU
The queue Length (AVCQU-SZ) can also be used as an indicator for measuring the system I/O load, but because Avcqu-sz is averaged over a unit time, it does not reflect instantaneous I/O flooding.
View disk IO status under Linux
