Questions tagged [iostat]

The iostat command is used for monitoring the CPU utilization and input/output load of devices attached to a system by observing the time the devices are active in relation to their average transfer rates.

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Understanding iostat with Linux software RAID

I'm trying to understand what I see in iostat, specifically the differences between the output for md and sd devices. I have a couple of quite large Centos Linux servers, each with E3-1230 CPU, 16 GB ...
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675 views

Why is the size of my IO requests being limited, to about 512K?

I read /dev/sda using a 1MiB block size. Linux seems to limit the IO requests to 512KiB an average size of 512KiB. What is happening here? Is there a configuration option for this behaviour? $ ...
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Does IOSTATS show output since boot or since last execution?

I see conflicting information online about use of IOSTAT. In particular I would like to be able to show an average since boot. Based on information I have read if I have never issued the command ...
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Understanding iostat block measurements

I am trying to understand how data is written to the disk. I'm writing data with dd using various block sizes, but it looks like the disk is always getting hit with the same size blocks, according to ...
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CPU error in iostat command

I need to create a Shell script to showing only the CPU error in iostat command for example I have two CPU c0d0 Soft Errors: 0 Transport Errors: 0 Protocol Errors: 0 Vendor: SUN ...
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How to find which disk is being written to/read from in an LSI HW RAID logical volume?

On this system there is a lot of "await" which is causing slow response. i need to find out which disk behind the LSI logical volume is slowing it down... IBM blade, 2 HDD with LSI RAID (LV simple ...
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lvm lv has different iostate with its pv at the same time

I noticed something strange on my machine on SUSE 12 My machine is on Azure and has three different disk(SSD) and using LVM. As I run iostat, I noticed that one lv has very high read ,while the pv ...
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Why is the iostat output only wait column high on Solaris 11?

When performing end backup on Oracle DB, lgwr has a 4000 millesecond delay. And.. Only wait and %w are high in the iostat result. extended device statistics r/s w/s kr/s ...
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NVMe disk shows 80% io utilization, partitions show 0% io utilization

I have a CentOS 7 server (kernel 3.10.0-957.12.1.el7.x86_64) with 2 NVMe disks with the following setup: # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme0n1 259:0 0 477G 0 ...
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How to get Disk Stats based on different parameters

Is there any way to get a disk stats grouped on certain params like: writes by size/latency? reads by size/latency? something like: total writes - 100 writes by size: - < 4096 - 20 - ...
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IO wait time is higher than disk utilization. Isn't this impossible? [duplicate]

I am trying to improve my understanding, following this (so far) unanswered question: Possible limiting factor during upgrade of Fedora VM - not disk or cpu or network? I ran the following test load, ...
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iostat: avoid displaying loop devices information

Given the annoying feature of snap's loop devices, my iostat output in an Ubuntu 18.04.02 is kind of like this Is there a way to filter out loop devices other than | grep -v loop ? $ iostat -xm ...
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How to find max queue length for device?

Recently I ran into some I/O overload problrms on some of our machines and I have been searching to find thresholds for some metrics like: avgqu-sz await svctm Then I saw this post on Stack ...
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where can I find the disk latency using iostat ( await, svctm, %util )?

I'm using Redhat Linux 6.5 and would like to see the disk latencies for the used disks. Using iostat I get the columns await and svctm ( including %util ). But according to the man page of iostat ...
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What does “no device” mean when running iostat -En

We presume to have a faulty cable that connects the SAN to a direct I/O LDOM. This is a snippet of the error when running iostat -En c5t60060E8007C50E000030C50E00001067d0 Soft Errors: 0 Hard ...
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953 views

Disk io stat “averaged” over a period of time

I am using the iostat utility on my RedHat Linux server to monitor the performance of a disk. When I use "iostat -xd sdh 1", I get the perf result printed every one second. When I use "iostat -xd sdh ...
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iostat: what is exactly the concept of merge

From iostat man pages: rrqm/s The number of read requests merged per second that were queued to the device. wrqm/s The number of write requests merged per second that were queued to the device. r/...
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How can I remove the headers

I would like to remove both headers (that are incidentally repeated). Any solution for it? [root@report]# iostat -xd 5 Linux 3.10.0-693.21.1.el7.x86_64 (mdds-pgbackup-01) 07/05/2018 _x86_64_ ...
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iostat - What does the 'steal' field mean?

In output of iostat there is a steal field, according to man page the field is used to: Show the percentage of time spent in involuntary wait by the virtual CPU or CPUs while the hypervisor was ...
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Install IOTOP/IOSTAT via ZYPPER (or anything else) on a SUSE (SLES) 12 Virual Machine (HyperV)

I have a virtual machine hosted on HyperV. It is a SUSE Enterprise 12 OS residing in a rack somewhere in the dark side of our office. This machine is under-performing during a certain load that takes ...
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Linux - Extracting Tar dramatically slows down server

I have a web server (specs below) with 12 TB of storage. I am moving massive amounts of csv files packaged in TAR's to the server, then extracting on the server. The problem is that when extracting ...
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Reading iostat utilization with ZFS zvols

First off, I asked this question 5 days ago over on Serverfault. I hope I'm not doing a bad by bringing it over here to the Unix&Linux Stack. I have also asked this question on 3 other sites not ...
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What is the difference between nfs_readpage and nfs_read?

Does every nfs_read always has a nfs_readpage request or does both are exclusive? Please explain. I am trying to understand this: http://www.fsl.cs.stonybrook.edu/~mchen/mountstat-format.txt
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how to query sar(sysstat) for more than one day data points

I don't see 'sar' command accepts date-and-time as starttime(-s) or endtime(-e) than just time. So, how to query 'sar' for more than one day's data point with older date and times(-f not going to help ...
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Remove system information from iostat command output

I am trying to get some I/O stats about the partitions on the system using iostat command as follows: iostat -d /dev/sda The output appears as follows: Linux 4.10.0-33-generic (test) Tuesday 26 ...
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Track total data written in and read from a folder within bash script

I have a bash script to do calculation. This calculation generates big scratch files as big as 12 GB and the disk usage of scratch folder is ~30 GB. I want to know how much total data is written to ...
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How to find process doing very high io read (without iotop)

By using iostat I see a constant 200+MB/s read on a certain device. How can I understand on CentOS which process is causing this, without using iotop (I cannot install it in this environment)?
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why linux cp command don't consume disk IO?

os: centos7 test file: a.txt 1.2G monitor command: iostat -xdm 1 The first scene: cp a.txt b.txt #b.txt is not exist The second scene: cp a.txt b.txt #b.txt is exist Why the first ...
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Execute command inside guest vm Libvirt

Is it possible to execute a command for eg:iostat inside a guest VM using libvirt or virsh .I want to find out IOPS for a guest vm but with libvirt java api I am not able to get the IOPS of a vm ,...
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Difference between 'sar' and 'iostat' commands

With sar and iowait, we can get CPU time utilization. But, when I executed both commands, I could see significant differences in their outputs. > iostat && sar 1 1 Linux 2.6.32-042stab090....
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Priority read and write files

Good day, I had a question that I could not find the answer. I tested my hard drive, mounted on /media/data using dd. Some simple scripts: write: echo "3" > /proc/sys/vm/drop_caches for i in {1....
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iostat disk utilization is full when there is no IO happening

I'm doing iostat on RHEL-6.6 machine and the results shown by 2 columns are difficult to understand. iostat -xm 1 result: avgqu-sz = a large number (42353468) %util = 100% There is absolutely no ...
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438 views

Is there a way to monitor disk i/o patterns? (i.e. random or sequential i/o?)

While an application is running, I can monitor disk bandwidth usage using linux tools including dstat. Now I'd like to know how many sequential or random disk I/Os are occurring in the system. Does ...
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Random write on DISK benchmark shows high read rate on iostat

I am running a random write benchmark directly on some disks (HDD & SDD) and I am getting some weird output data on the iostat monitor. Besides the usual write rate, there is a read rate that I ...
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Getting averageReadTime and averageWriteTime in solaris(disk I/O)

I am working on getting 'Average read time (ms)' and 'Average write time(ms)' from "iostat -xnp" command. In linux there is a '/proc/diskstats" command, which gives me 'Time spent in reading millis' ...
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IOSTAT report doesn't match with DD benchmark

I am running a DD benchmark but the obtained results are not matching with the IOSTAT values. This is the DD sample: $ sudo dd bs=4096 count=690 if=/dev/zero of=/mnt/tmp/test oflag=dsync 690+0 ...
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iostat ( column svctm is not trusted any more ) what to use instead?

I'm running a Linux Server with "Oracle Linux Server release 6.5" which is pretty much the same as RedHat Version. I need to determine the latency on my disk devices. The man page of the iostat ...
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Trying to understand iostat for simple sequential read case

I'm looking at the disk I/O performance of a web hosting VPS (virtual server) and I'd like help in understanding the figures that 'iostat' is giving me. This is my very simple sequential read of the ...
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How can I get read/write instant speed of a Hard Drive using /proc/diskstats data?

I know that the proc/diskstats file presents these data columns: 1 - major number 2 - minor mumber 3 - device name 4 - reads completed successfully 5 - reads merged 6 - sectors read 7 - time spent ...
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Software raid problem

We have a software raid on our server and we have a problem with disk performances. From time to time disk i/o freezes. During those periods iostat shows that one disk is faster than another. Both ...
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Why doesn't my IOstat change its output at all?

My IOstat doesn't change...at all. It'll show a change in blocks being read and written, but it doesn't change at all when it comes to blocks/kB/MB read and written. When the server sits idle...it ...
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How can I find the CPU resource utilization of a process and all its children [duplicate]

If I have a process that spawns child processes, is there a good way to get a single number representing the combined CPU use of that process and its children? i.e is there a simple shell command ...
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566 views

Current disk load

I'm using iostat to get the current disk load each second with iostat -dx 1 (specially, %util column). However, I'd like to put this in a bash script and control the interval with the watch command ...
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iostat error counters on Solaris

In a Solaris system i use iostat -E and kstat to identify faulted disks. My problem is that I don't know if the problem is on disk, on controller, on bus or on the filesystem layer (ZFS). The key is ...
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iostat am I okay?

This is the result of iostat avg-cpu: %user %nice %system %iowait %steal %idle 13.65 0.00 9.98 3.86 2.22 70.29 Device: rrqm/s wrqm/s r/s w/s rkB/s ...