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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.

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. Reports generated by iostat are commonly used to improve the balance of the input/output load between physical disks.

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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 the columns svctm are obsolete and should not be…
Blockdump
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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 scene don't consume IO, but the second scene…
tairyao
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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 ,hence another method would be to execute a command…
arpit joshi
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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 servicing another virtual processor. But what does…
Eric
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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? $ sudo dd iflag=direct if=/dev/sda bs=1M of=/dev/null…
sourcejedi
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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/s The number (after merges) of read requests…
pkaramol
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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 the TAR files, the server become so slow that it's…
lessharm
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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 any one know any ways to achieve this?
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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 records in 690+0 records out 2826240 bytes (2,8 MB)…
Gustavo Portela
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IO wait time is higher than disk utilization. Isn't this impossible?

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, which took 200 seconds to complete. sudo perf…
sourcejedi
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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 5", I get the perf result printed every five…
Ahmed
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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 shows 363kB_read/s, 537kB_wrtn/s. If I put it under…
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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 2.6.32-042stab090.4 (LinuxBox) 08/14/2014 _x86_64_ (16…
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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 RAM and 4 2TB SATA disk drives. Most are JBOD,…
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Process shows as 100% I/O bound while producing minimal disk activity, disk util is at 100%

We are having quite strange problem. There is a program (cryptocurrency node to be precise) which has local database of all the transactions ever made. Database is huge - around 15 TB. The problem is that the program won't synchronize with the…
DimaA6_ABC
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