Questions tagged [iostat]

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iostat 100%util when not reading/writing much

I have a standalone server that recently started to produce strange data in the iostat command output. I likes to go up to 100% util while the r/s,w/s,rMB/s,wMB/s are relatively low. During that ...
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System performance of Rasperry Pi (running k8s) is very poor - how to debug?

Summary I'm running a slim homelab (Kubernetes cluster with few pods, Gitea, Drone, Docker Registry, and NFS share) on a 2-Pi4 cluster, and the system performance is poor. I've noted that the ...
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High util iostat

I have server with oracle db. It works on Dell Unity storage. The server has very slow disk IO. How can I fix it? Here are some details of my server: OS - OL8 Kernel - 5.4.17 uek Storage - Dell ...
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HP DL380 G8 - P420i Raid Controller - How to monitor physical disks on a slow hardware raid volume?

There is an HP DL380 G8 server with P420i Raid Controller, containing a RAID5 volume. It suddenly became slow, but all physical disks are ok. [root@localhost ~]# ssacli ctrl all show config detail ...
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High I/O wait in apache tomcat server

Facing high I/O wait in apache tomcat server when the load increases. Suspecting disk I/O is less when tomcat is running however. disk IO seems drops drastically when tomcat is running along with the ...
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How to determine disk is busy or not in oracle Linux?

I am confused, what is the command I can use to determine disk busy in Oracle Linux?. In Solaris iostat command will show %b. What is the command in Oracle Linux to show %b like in Solaris? Please ...
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3 votes
1 answer
75 views

Is the sum of IOPS for individual physical disks not equal to the raid0 logical disk?

I have a raid0 set up consisting of 2 physical disks: bash-4.2$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT xvda 202:0 0 100G 0 disk `-xvda1 202:1 0 100G 0 part / nvme0n1 259:...
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1 answer
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Is iostat unreliable?

I have noticed something worrying with iostat that I can't quite explain - it appears iostat may not be quite reliable(?) I'm trying to troubleshoot poor MySQL performance, and one ovious place to ...
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why iostat not showing one of my disk?

Please check the picture below. The df shows /dev/xsda mounted But iostat not showing the device. Why? [admin] /dev]$df -h | grep '/dev' tmpfs 64M 0 64M 0% /dev /dev/nvme1n1 7.0T ...
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1 answer
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Are my drives being utilized equally with Linux Software RAID 0 array?

I have four NVMe drives in a RAID 0 configuration. I am attempting to determine how many IOPS the array is handling. When I run iostat, it appears that one drive is handling more IO than the other ...
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3 votes
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199 views

Can iostat output show mismatched read data for mdadm raid5 array?

I'm trying to understand this iostat output: tps kB_read/s kB_wrtn/s kB_dscd/s kB_read kB_wrtn kB_dscd Device 500.30 58.9M 19.4k 0.0k 329.1G ...
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2 votes
2 answers
781 views

What could cause high iostat await if a disk isn't overutilized?

I have a database running on GCP. Occasionally it gets very slow for a period of minutes (like average statement execution time spikes by 10x or more). The slowness is correlated with increases in the ...
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iotune qemu/KVM total_iops total_bytes limits

I have created some qemu/KVM virtual machines on SSDs. The host has ~6 SSDs. 1 is being used for the OS, and each of the other SSDs has two VM guests. I'm using iotune to limit the capabilities of ...
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How does avgqu-sz size in iostat output relate to r_await and w_await?

Can someone explain what does avgqu-sz mean in the output of iostat? The manual page states like this. avgqu-sz: The average queue length of the requests that were issued to the device. Can ...
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Difference in utilisation reported by iostat for two identical disks in RAID1

I'm trying to debug some weird behaviour with Postgres performance and am trying to understand the iostat output. I'm on 2x SSD on RAID1. Why would one of the disks be reported at ~21% utilisation ...
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1 answer
377 views

iostat %util for NFS mounted shares available?

Is there a way to calculate, from the client, the "% util" of NFS mounted disks? I know with iostat, with locally mounted disks you can see %util Device: rrqm/s wrqm/s r/s ... ...
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1 answer
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What does iostat show a different utilization for the 'dm' device?

I installed an M.2 drive into a Proxmox host this morning and monitored the disks with iostat -x 1. Why is iostat showing dm-7 is at 98% utilization, while the M.2 LVM PV (nvme0n1p1) shows only 6.8? ...
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1 answer
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What are the parameters in iostat

I used iostat and trying to understand the iostat output using this link : https://linoxide.com/linux-command/linux-iostat-command/ but It is not clearly explained. PF the output at different times ...
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1 answer
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How to find good state io stats?

I would like to monitor disk I/O activity in case something courses heavy I/O. This Nagios plugin seams simple, where he gives examples of Example: Tps, read and write thresholds: ./...
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1 vote
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iostat showing wait queue when device is not 100% busy

I am on Solaris 11 and I am seeing the following %w=32 %b=62 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 47.5 2564.6 1460.1 33481....
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3 answers
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modify iostat -t time output format

I was trying to plot the results of various iostat results. For that I want to use https://clusterbuffer.wordpress.com/file-system-tools/iostat_plot/iostat-plotter-v3/. Anyhow - for some ...
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0 votes
2 answers
86 views

How to determine if I/O is slow for server

I have used I/O stat to check whether my server's I/O is slow or not. The % util is high but so is the read/sec - write/sec. Can anyone help ? Following is the output of iostat -mx command Linux 2.6....
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2 votes
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Resetting disk table in zfs pool

In Our Solaris 11.3 zfs storage server, one disk in the pool died, we replaced it. Everything is working fine, but iostat is still showing old disk with large error count. This is bothering our ...
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3 votes
1 answer
1k views

Why are cpu usage percentage different between top and iostat?

On a heavily loaded database server, I am getting vastly different output from top and iostat for cpu usage. Why might the value be different? top: %Cpu(s): 84.7 us, 11.8 sy, 0.3 ni, 2.4 id, 0.6 ...
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How to get gcc installed on CoreOS hostmachine rather than the containers running inside it

I have an external monitoring tool that connects over ssh periodically and checks the various system params of a linux box (cpu, mem, etc.). However this approach does not work with CoreOS since it ...
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11 votes
1 answer
6k views

(A Windows guy asks) Measuring Disk Latency on Linux: Do I bother?

On Windows, whenever I want to validate / confirm that there might be IO-related issues on a volume that a database or other low-latency app lives on, I check disk latency. If I see the Windows ...
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0 votes
3 answers
914 views

e2fsck takes lot of time to run

I am running e2fsck on one of my disk partitions (ext4) but it seems to take eternity. It is already running now for almost 10 hours or so and it is still at 42%. The size of the partition is around ...
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Nagios php script to read iostat values

I'm working on a php script(nagios plugin) to read r/s,w/s,rMB/s,wMB/s,%util from the iostat command, e.g. #iostat -xm sda avg-cpu: %user %nice %system %iowait %steal %idle 1.05 0....
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2 votes
2 answers
201 views

physical vs logical disk transactions

I'm trying to analyze server requirements for a set of virtual machines. We're using LVM on them, so iostat shows numbers for both the logical volume and the physical disk, and they often don't match ...
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1 vote
1 answer
648 views

Linux "iostat" to .csv file using Perl

I am experimenting with the iostat -c 1 command, and I was wondering if there is a simple way of reading the current output and then separating the values so that I could generate a .csv file. The ...
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1 vote
1 answer
826 views

NFS read/writes since startup

I'd like to retrieve the total number of kilobytes read/written for each NFS mount point. Using the following commands, I'm able to see the current throughput for each NFS mount point in kB/S. ...
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Bytes read / written SNMP value differs from iostat

I am trying to monitor my server over SNMP and UCD-DISKIO-MIB::diskIONRead.1 gives me 1344574464 while iostat reports 9701669 kB_read. Why the discrepancy? I don't have to mention that I am monitoring ...
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No w/s in iostat output even though wMB/s is high

I am trying to format a 2 TB SAN based block device (/dev/mapper/mpathb). Even though, mke2fs has been running since over one hour without completing, iostat -z -x -m 10 output in a separate terminal ...
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2 votes
1 answer
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HP UX iostat on File System

I have a server running HP UX 11 OS and I'm trying to have I/O statistics for File System and not disk. For example, I have 50 disk attached to the server when I type iostat (here under output of ...
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3 votes
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Why are /proc/diskstats figures suddenly unbelievably low?

I have a Debian jessie server with two Intel DC S3610 SSDs in it, in RAID-10. It's reasonably busy for IO and for the last several weeks I've been graphing the IOPS: As you can see, most of the time ...
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How many milliseconds of await is considered to be high? [closed]

How many milliseconds of await is considered to be high? i have 800ms and 600ms iostat -x avg-cpu: %user %nice %system %iowait %steal %idle 1.28 0.00 0.22 0.90 0.00 ...
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10 votes
1 answer
25k views

what percentage of iowait is considered to be high?

when iowait is considered to be high ? iostat -x avg-cpu: %user %nice %system %iowait %steal %idle 2,89 0,01 5,45 49,83 0,00 41,83 Device: rrqm/s wrqm/s ...
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771 views

Not getting Proper output for check_iostat for nrpe plugins

My iostat is giving following output $ iostat Linux 3.13.0-29-generic (Inksedge) 08/13/2015 _x86_64_ (4 CPU) Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn xvdap1 ...
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0 votes
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299 views

Interpreting the IOstat result

Below are the results for iostats: Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn sda 120.94 10201.14 4354.87 64513033284 27540653120 sdb 63....
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2 votes
1 answer
55 views

iostat taking lot of time to return

I have a solaris 10 server with a lot of SAN disks (close to 1000 across all paths). iostat -En takes close to 5 min to return. Is there a way to figure out what is causing the delay? truss hasn't ...
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1 vote
2 answers
1k views

How to interpret iostat for a crumbling MySQL server

We have a combined application/MySQL-server which has started to crumble. Right now, it gets stuck on copying a 125 million row MySQL MyISAM table (INSERT INTO a_copy SELECT * FROM a with KEYS ...
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1 vote
1 answer
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What is the difference between rMB_nor/s, rMB_dir/s, and rMB_svr/s in iostat?

I'm trying to interpret the results of running the following command iostat -mnhyc It produces the following Filesystem: rMB_nor/s wMB_nor/s rMB_dir/s wMB_dir/s rMB_svr/s ...
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slow file server with contradictory values for CPU and CPL in atop

I've got a fileserver (centos 6.3) that slowed down suddenly earlier today. The cluster that mounts it could access other NFS mounts without a problem, but the access to this one was VERY slow. ...
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-1 votes
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iostat reporting low r/s on first line for specific disk, expected r/s on all following lines for that same disk

When copying data from hard disk sdc to sda, I notice that the number of read requests completed per second was unusually low: $ iostat -x 1 1 Linux 3.13.0-32-generic (melancholy) 2014-08-15 ...
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Get I/O TPS for NFS on Solaris machines

I'm attempting to get IOPS for my Solaris servers. Typically I use tps for this calculation, however: iostat gives TPS but only for local disks. iostat -x gives everything but TPS for ALL disks. sar -...
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9 votes
1 answer
15k views

Windows "iowait" CPU utilization reporting

Does Windows account for and report "iowait" in the same manner as Linux? That is, processes enter "uninterruptible sleep" and their time spent is subtracted from "CPU free"? If so, which Perfmon ...
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3 votes
2 answers
1k views

Reporting historical system activity in FreeBSD

I'd like to record data about system activity under FreeBSD for future analysis. If I were running a SysV system, I'd just sar and its related utilities, but that doesn't exist in the BSDs. (And ...
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1 vote
1 answer
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Strange iostat numbers

I'm experiencing unusual load issue on one of our VM which is on SAN storage. As a general practice I ran iostat on the server got very strange numbers. avg-cpu: %user %nice %system %iowait %...
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1 vote
1 answer
1k views

iostat to analyze iSCSI mount

Is there a way to analyze the IO wait on a iSCSI mount from the machine on which the iSCSI share is mounted? I understand the local volumes can be analyzed, but, we have one particular directory on ...
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MySql/RedHat, High I/O Wait ... for a few hours... then disappears

I've got a RH server as a VMWare instance logging GPS fixes 24x7. The transaction volume hasn't changed over the months (in fact I am pruning the transaction table more aggressively now) with only ...
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