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I am working on a new IO scheduler for the Linux Kernel. I am trying to see if anyone knows of a tool that prints out total number of outstanding IO requests (Disk IO queue) in Linux?
I would be working from a terminal.
Thank you!
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By using iotop command, you can monitor the disk utilization by individual processes. You will get the following output: By typing the iotop command with o option, you will get the actual I/O activity. With the help of iostat command, you will get the individual hard disk I/O activity.
Disk Queue Length, the higher the number the more disk operations are waiting. It requires attention if this value frequently exceeds a value of 2 during peak usage of SQL Server. If you have multiple drives you should take this number and divide by the number of drives in the array to see if the number is above 2.
The best way to check disk IOPS in Linux is using a command-line tool called iostat. This tool is part of the sysstat package, which is a collection of Linux system monitoring tools. The iostat command is used to monitor disk workload in real-time.
Forgive the massive necro here. You actually want iostat -x which will display the extended stats for the device in question since last iostat was run. If you wish to monitor the queue in realtime you want iostat -xt 1 (or iostat -xmt 1 to show details in megabytes).
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.
18/05/15 00:41:05
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 0.00 6.02 0.00 93.98
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
xvda 0.00 0.00 1.00 1308.00 0.00 163.50 255.81 133.30 101.15 0.76 100.00
dmitry@pro:~$ iostat
disk0 cpu load average
KB/t tps MB/s us sy id 1m 5m 15m
50.70 34 1.70 4 3 93 1.83 1.65 1.70
dmitry@pro:~$
DESCRIPTION Iostat displays kernel I/O statistics on terminal, device and cpu opera- tions. The first statistics that are printed are averaged over the sys- tem uptime. To get information about the current activity, a suitable wait time should be specified, so that the subsequent sets of printed statistics will be averaged over that time.
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