Iostat, iostat-x

Iostat, iostat-x

In Linux, performance problems occur. Generally, we can use top. iostat, vmstat, and other commands to locate the problem. Iostat can provide us with rich IO status data.
$ Iostat-x-1

Avg-cpu: % user % nice % system % iowait % steal % idle

10.43 0.00 1.51 1.51 0.00 86.56

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm % util

Sda 4477.00 9.00 951.00 13.00 24288.00 2492.00 55.56 0.21 0.22 0.21 0.92 0.17 16.00

% User: Show the percentage of CPU utilization that occurred while executing at the user level (application ).

% Nice: Show the percentage of CPU utilization that occurred while executing at the user levelwith nice priority.

% System: Show the percentage of CPU utilization that occurred while executing at the system level (kernel ).

% Iowait: Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request.

% Steal: Show the percentage of time spent in involuntary wait by the virtual CPU or CPUs while thehypervisor was servicing another virtual processor.

% Idle: Show the percentage of time that the CPU or CPUs were idle and the system did not have an outstanding disk I/O request.

Rrqm/s: the number of merge read operations per second. That is, delta (rmerge)/s wrqm/s: Number of write operations performed on merge per second. That is, delta (wmerge)/s r/s: The number of read I/O devices per second. That is, delta (rio)/s w/s: the number of write I/0 devices completed per second. That is, delta (wio)/s rsec/s: Number of read sectors per second. That is, delta (rsect)/s wsec/s: Number of write sectors per second. That is, delta (wsect)/s rKB/s: the number of read K bytes per second. It is half of rsec/s, because the size of each slice is 512 bytes wKB/s: the number of K bytes written per second. Half of wsec/s avgrq-sz: average data size (slice) of each device I/O operation ). That is, delta (rsect + wsect)/delta (rio + wio) avgqu-sz: Average I/O queue length. That is, delta (aveq)/s/1000 (because aveq is measured in milliseconds) await: average wait time (in milliseconds) for each device I/O operation ). That is, delta (ruse + wuse)/delta (rio + wio) svctm: Average service time per device I/O operation (MS ). That is, delta (use)/delta (rio + wio) % util: the percentage of time in one second for I/O operations, or the number of I/O queues in one second is not empty. That is, delta (usr)/s/1000 (because the Unit of use is milliseconds)
If % util is close to 100%, it indicates that there are too many I/O requests, the I/O system is fully loaded, and the disk may have a bottleneck. Generally, if % util is greater than 70%, the I/O pressure is relatively high.
Generally, svctm is smaller than await (because the wait time for simultaneously waiting requests is calculated repeatedly). The size of svctm is generally related to disk performance, and the CPU/memory load will also affect it, too many requests may indirectly increase the svctm. The size of await generally depends on the service time (svctm), the length of the I/O queue, and the mode in which I/O requests are sent. If svctm is close to await, it means that I/O has almost no waiting time. If await is much larger than svctm, it means that the I/O queue is too long and the response time of the application is slow, if the response time exceeds the allowable range, you can consider replacing a faster disk, adjusting the kernel elevator algorithm, optimizing the application, or upgrading the CPU.
The queue length (avcqu-sz) can also be used as an indicator to measure the system I/O load, but because avcqu-sz is based on the average per unit time, therefore, it cannot reflect the instantaneous I/O flood.

Check the physical size of the hard disk under solaris. Why is the total size smaller than the total size of the disk viewed with df-h by using the iostat-E command?

Iostat-ecan view the size of all disks and error statistics on each disk (Expansion device).-E: report extended device error statistics

Df-h is used to view the current system partitions. Generally, only mounted partitions are displayed.

A physical hard disk can be mounted and divided into multiple partitions. In df-h, it can be listed as multiple rows. If no hard disk partition is mounted, df-h cannot be used.

Bash-3.00 # iostat-E
Sd0 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: SEAGATE Product: ST973402SSUN72G Revision: 0603 Serial No: 090723 MPVA
Size: 73.41 GB <73407865856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 3 Predictive Failure Analysis: 0
Sd1 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: SEAGATE Product: ST973402SSUN72G Revision: 0603 Serial No: 090723 MPSX
Size: 73.41 GB <73407865856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 2 Predictive Failure Analysis: 0
Sd2 Soft Errors: 0 Hard Errors: 0 Transport Errors: 1
Vendor: TEAC Product: DW-224SL-R Revision: 1.0B Serial No:
Size: 2.28 GB <2278031360 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 9 Predictive Failure Analysis: 0

Check the physical size of the hard disk under solaris. Why is the total size smaller than the total size of the disk viewed with df-h by using the iostat-E command?

Iostat-ecan view the size of all disks and error statistics on each disk (Expansion device).-E: report extended device error statistics

Df-h is used to view the current system partitions. Generally, only mounted partitions are displayed.

A physical hard disk can be mounted and divided into multiple partitions. In df-h, it can be listed as multiple rows. If no hard disk partition is mounted, df-h cannot be used.

Bash-3.00 # iostat-E
Sd0 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: SEAGATE Product: ST973402SSUN72G Revision: 0603 Serial No: 090723 MPVA
Size: 73.41 GB <73407865856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 3 Predictive Failure Analysis: 0
Sd1 Soft Errors: 0 Hard Errors: 0 Transport Errors: 0
Vendor: SEAGATE Product: ST973402SSUN72G Revision: 0603 Serial No: 090723 MPSX
Size: 73.41 GB <73407865856 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 2 Predictive Failure Analysis: 0
Sd2 Soft Errors: 0 Hard Errors: 0 Transport Errors: 1
Vendor: TEAC Product: DW-224SL-R Revision: 1.0B Serial No:
Size: 2.28 GB <2278031360 bytes>
Media Error: 0 Device Not Ready: 0 No Device: 0 Recoverable: 0
Illegal Request: 9 Predictive Failure Analysis: 0