How to Measure Your Disk Activity for Linux Web Server

1. How do I see Disk activity in Linux?
2. How do I check disk IO utilization in Linux?
3. How do I check my Iowait?
4. How do I check my disk IOPS?
5. What is disk I O in Linux?
6. What is Linux load average?
7. How do you read Iostat output?
8. How use iostat command in Linux?
9. What is Iowait in SAR output?
10. What is CPU wait time?
11. What is CPU wait in Linux?
12. How do I find disk queue length in Linux?
13. How many IOPS does a VM need?

How do I see Disk activity in Linux?

5 Tools for Monitoring Disk Activity in Linux

1. iostat. iostat can be used to report the disk read/write rates and counts for an interval continuously. ...
2. iotop. iotop is a top-like utility for displaying real-time disk activity. ...
3. dstat. dstat is a little more user-friendly version of iostat , and can show much more information than just disk bandwidth. ...
4. atop. ...
5. ioping.

How do I check disk IO utilization in Linux?

Run the iotop command without any arguments, to see each process or threads about current I/O usage. To check which processes are actually utilizing the disk IO, run the iotop command with -o or –only option to visualize it. Details: IO: It shows Input/Output utilization of each process, which includes disk and swap.

How do I check my Iowait?

iotop – top-like I/O monitor. Try it with the -oPa options to show the accumulated I/O of active processes only. ps – use auxf , then under the “STAT” column “D” usually indicates disk iowait.

How do I check my disk IOPS?

Run a Perfmon using Physical Disk:Reads/sec, Physical Disk:Writes/sec, Physical Disk:Write Disk Queue. A high disk queue means the OS is waiting for time to write to the disk. The writes/reads will tell you what your IOPS are currently running.

What is disk I O in Linux?

One of the common causes of this condition is disk I/O bottleneck. Disk I/O is input/output (write/read) operations on a physical disk (or other storage). Requests which involve disk I/O can be slowed greatly if CPUs need to wait on the disk to read or write data.

What is Linux load average?

The load average is the average system load on a Linux server for a defined period of time. In other words, it is the CPU demand of a server that includes sum of the running and the waiting threads.

How do you read Iostat output?

To interpret the output of iostat, you need to know a little performance terminology:

1. Throughput is the rate at which a system completes operations, in units of operations per second.
2. Concurrency is the number of operations in progress at a time, either as an instantaneous measure or an average over an interval of time.

How use iostat command in Linux?

The iostat command in Linux is used for monitoring system input/output statistics for devices and partitions. It monitors system input/output by observing the time the devices are active in relation to their average transfer rates.

What is Iowait in SAR output?

Following is the definition taken from the sar manpage: %iowait: Percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request. Therefore, %iowait means that from the CPU point of view, no tasks were runnable, but at least one I/O was in progress.

What is CPU wait time?

CPU wait is a somewhat broad and nuanced term for the amount of time that a task has to wait to access CPU resources. This term is popularly used in virtualized environments, where multiple virtual machines compete for processor resources.

What is CPU wait in Linux?

For a given CPU, the I/O wait time is the time during which that CPU was idle (i.e. didn't execute any tasks) and there was at least one outstanding disk I/O operation requested by a task scheduled on that CPU (at the time it generated that I/O request).

How do I find disk queue length in Linux?

You can see the average queue size in the aqu-sz column (in previous versions avgqu-sz ). Consider the following example output from iostat -xmt 1 which shows a full IO queue (max queue length is 128 for this device) and a saturated disk during a benchmark.

How many IOPS does a VM need?

Storage IOPS density and keeping your user's sanity

Thus a typical VM with 20-40 GB disk will get just 3 to 6 IOPS. Dismal. 50-100 IOPS per VM can be a good target for VMs which will be usable, not lagging. This will keep your users happy enough, instead of pulling their hair.