Questions tagged [iowait]
The iowait tag has no usage guidance.
72
questions
1
vote
0
answers
166
views
How to deal with uninterruptible processes due to CIFS mounted filesystem
I am observing very high IOWAIT time on the CPUs of my server:
top - 14:24:20 up 846 days, 14:14, 2 users, load average: 14.42, 14.33, 14.57
Tasks: 345 total, 1 running, 341 sleeping, 3 stopped, ...
- 27
0
votes
1
answer
279
views
High I/O wait and Context Switches - how to debug
Update:
sar -W -B -d output added to bottom of post.
I have simulated this on boot. I have uwsgi starting 9 instances of a django app, along with gunicorn for websockets, and dramatiq for queue ...
- 123
0
votes
1
answer
210
views
High iowait causing problems
Since a week I've been suffering from a server with VPS servers that is very slow and has a lot of IOWAIT. Can someone explain or tell what is causing this problems?
Command: iotop -aoP
PID PRIO ...
- 1
0
votes
2
answers
828
views
High iowait, swap nearly always fully in use
I'm often experiencing slowness on a large server that is used by several users simultaneously, with many CPUs (72) and a decent amount of ram (125gb).
Granted, the server runs a lot of stuff so gets ...
- 101
0
votes
0
answers
2k
views
100% CPU usage from iowait caused by Nginx, not solved by turning sendfile on and directio off
I run a webservice that performs some basic image processing operations.
The webserver first accepts image uploads from users and temporarily stores them. A backend server then downloads the image ...
- 1
0
votes
0
answers
704
views
Finding source of high IOWait
I have a 5 node elasticsearch cluster. One host has had consistently high IOWait% (40+) for several weeks. The others seem fine (<10%).
Notable:
Host in question is not the cluster master
New ...
- 2,341
2
votes
1
answer
2k
views
RHEL8: Does NFS I/O count as part of "%iowait" calculations?
Customer telling us that they see high %iowait in top and iostat output on a busy RHEL8 NFS client.
iostat man page clearly says that iowait is related to % of time kernel is waiting on "disk&...
- 141
0
votes
2
answers
683
views
High iowait with RAID0. CPU 100%. Static data is not cached in RAM
I ask for your help.
I myself can no longer see the way out.
I have a server
1x Xeon E-2236
32RAM
4 x 10TB disks (WDC WD101KRYZ-01) - collected in RAID-0.
The disks are fast. Each individually ...
0
votes
0
answers
104
views
75% CPU wait and apt upgrade hanging
Recently I observed a relatively constant 7/8 (core) load on one of my servers. Looking with top, seems that CPU is constantly 75% waiting:
Tasks: 401 total, 1 running, 400 sleeping, 0 stopped, ...
- 51
1
vote
1
answer
977
views
One process takes all server resources (iowait?)
I have multiple processes running simultaneously on the same box under CentOS 7 (each one on behalf of the separate Linux user).
I use Zabbix for monitoring.
Sometimes the following pattern ...
- 123
2
votes
3
answers
2k
views
Apache 2 handling requests very slow after Restart
We have a GPS device socket handling server using NodeJS which sends the received HTTPS request to Apache installed server and saving the data into MySQL Database. When we restart NodeJS or Apache ...
- 23
0
votes
1
answer
437
views
Iowait on single HDD drive slows/blocks operations on all other (SSD) drives on a DELL R620 w/ PERC H310 Mini Mono controller
As the Dell forums are a veritable disaster I'm trying here in case somebody has some hints for me here :)
We have a system with 3 drives:
SSD for the OS
SSD containing a ZFS pool backing LXD ...
- 75
0
votes
1
answer
296
views
iowait Bound Server - Load Calculations & Process Scheduling
I have a script I'm writing that runs badblocks against a disk shelf full of drives and I'm trying to understand the server load that develops and at what point the server load is critical in this ...
- 66
3
votes
4
answers
2k
views
MySQL on VM, High IO Wait but low TPS
We are trying to figure out a strange situation on our MySQL installation on VM. We are on Mysql 5.7 and RHEL 7 with XFS.
We are observing when we run a few select queries the IOWait races up to 40-...
0
votes
1
answer
513
views
glusterfsd Ubuntu 18.04 high iowait issues
We're running gluster on two hypervisors running Ubuntu. When we upgraded from Ubuntu 14.04 to 18.04, it upgraded gluster from 3.4.2 to 3.13.2. As soon as we upgraded and since then, we've been seeing ...
- 121
1
vote
0
answers
1k
views
What is a "normal" latency/performance of inserts on mariadb or mysql?
Hadn't used MySQL family for years. Now need to move from OracleDB to either MariaDB or PostgreSQL.
So on a similar "hardware" (Openstack VM: RHEL 7.3, 4HT cores of 2.5GHz Xeon E312xx, "local" SAN &...
- 107
0
votes
0
answers
100
views
Tool to generate IOWaits
In order to test our monitoring infrastructure, I'd like to generate enough IOs to trigger an alert. As the alert is based on IOWaits, I should find a way to 'overload' the IOs.
I found an article ...
- 293
1
vote
0
answers
741
views
Issues with sudden high iowait on RabbitMQ Cluster
we run a RabbitMQ Cluster with 6 c5.2xlarge nodes on AWS. The Version is 3.6.14 on Erlang 19.1. They run in docker containers and mount a local volume to /var/lib/rabbitmq/mnesia.
The docker run ...
- 11
0
votes
1
answer
786
views
CPU wait state (RAM) stats?
As far as I understand, the wa % stat displayed by top is the I/O wait (i.e. hard drive).
Is there a way to get similar wait stats, but for when the CPU is waiting for memory?
My server is pretty ...
- 4,607
-1
votes
1
answer
3k
views
What exactly is IOWait [duplicate]
I know that the IOWait metric is the amount of time that a cpu is waiting for IO.
As I understand it IOWait always refers to disc io. But why is that? Why doesn't network IO, presumably involving ...
- 133
0
votes
0
answers
934
views
Linux ext4 timeout in KVM guest
Both the host OS and the guest OS are Debian 8 amd64. The guest is a raw disk image stored at /srv/machines/web.img. The host has a backup script scheduled each night at 1:55am. Here is my backup ...
- 250
1
vote
0
answers
1k
views
qemu-kvm VM hangs at iowait with virtio drive
We are seeing instances of a VM hanging with the following symptoms:
load average 800, processes stuck, CPU 100% in iowait
reading files work, writing files hang the system
RAM utilization is high, ...
- 111
4
votes
2
answers
2k
views
Can increased disk throughput increase CPU utilization?
We recently upgraded the storage in our data center and migrated all our production systems to it. We noticed that in one machine (an HP_UX IA-64 Oracle database server for SAP), the CPU utilization ...
- 361
3
votes
2
answers
5k
views
Drawbacks of setting a high I/O timeout?
I'm working on several Linux VMs whose partitions are mounted on a NetApp NAS. This NAS periodically experiences a very high iowait which causes the VM disks to switch to read-only mode, crash, or be ...
- 1,105
1
vote
3
answers
8k
views
MySQL and high jdb2 io/wait
I am running MySQL 5.5 with InnoDB tables. There are about 200 queries per second. There are also tables with 500 000 or more rows. But I have big issues with server load and io/wait especially with ...
- 29
12
votes
1
answer
29k
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 ...
- 317
20
votes
1
answer
3k
views
Why higher await time for DM multipath device than underlying device?
We have a CentOS 6.4 based server attached to Hitachi HNAS 3080 storage and observed the kernel remount the filesystem in read-only mode:
May 16 07:31:03 GNS3-SRV-CMP-001 kernel: [1259725.675814] ...
- 778
0
votes
0
answers
1k
views
Linux high iowait without block device activity
I'm having a hard time figure out the reason cause high iowait on my server.
top:
%Cpu(s): : 30.0 us, 5.4 sy, 0.0 ni, 53.9 id, 10.1 wa, 0.0 hi, 0.7 si, 0.0 st
iostat:
Device: rrqm/s ...
- 53
-2
votes
1
answer
797
views
High IO wait when test disk with dd
My server is using two SATA disk Raid 1. I test disk using dd
#!/bin/bash
i=0
MAX_LOOP=10
while [ $i -lt $MAX_LOOP ]
do
dd if=/dev/zero of=/data/output bs=1G count=10
((i++))
done
...
- 111
2
votes
2
answers
233
views
Would software RAID0'ing SSDs help or hinder maximization of useful CPU work throughput?
My question is in the title... here is some background:
[OS is Linux.]
[UPDATE: The contents of this RAID0 is redundant (sync'd from SCM). I am not worried about the increased risk of data loss.]
...
- 133
1
vote
1
answer
1k
views
Monitoring/Warning for IOWait
I had a downtime today on my server because of a high IOWait. I could not do mostly anything on the server, I managed only to run top to see the IOWait, but I did not have iotop installed at that time,...
- 295
0
votes
2
answers
428
views
Apache not serving static content concurrently
When tried to open multiple pages from Codeigniter based custom CMS on different tabs, the first tab loads, while the subsequent tabs wait for the first tab to complete, then sequence follows randomly,...
- 131
0
votes
2
answers
2k
views
High iowait despite small amount of write/read
I'm not sure how to interpret this or the next steps, but why is IOWait so high when I have not written/read much from any devices?
Background: I am a developer trying to find why the DB seems to be ...
- 431
3
votes
1
answer
11k
views
CentOS6 and long Wait IO time on jbd2/dm-0-8
Linux box running CentOS 6.5 and 2.6.32-431.3.1.el6.i686 kernel recently got CPU spikes up to 99% causing by Wait IO.
Executing
while true; do date; ps auxf | awk '{if($8=="D") print $0;}'; sleep 1; ...
- 391
0
votes
1
answer
579
views
Full core of iowait with no actual IO load
I'm having an issue with a box that is "randomly" gaining an entire core worth of iowait -- and as far as I can tell there isn't any IO load to go with it, as illustrated by iostat:
avg-cpu: %user ...
- 176
0
votes
1
answer
836
views
iowait high when uncompress file in EC2 instance (AWS)
this 2 days, i faced very weird problem.
When i'm doing uncompress big file, the iowait become very high, more than 70%
I do iotop and the result got 3 process with high IO
gzip -d filename
[flush-...
- 3
10
votes
1
answer
17k
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 ...
- 656
0
votes
1
answer
2k
views
Tracing down High Linux Load - HDD at fault or too many interrupts ? (ksoftirqd Time 437:44.13)
Server Stats:
"cat /proc/version" Output
Linux version 2.6.18-308.24.1.el5 ([email protected]) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-52)) #1 SMP Tue Dec 4 17:43:34 EST 2012
...
- 202
5
votes
3
answers
5k
views
Strange Recurrent Excessive I/O Wait
I know quite well that I/O wait has been discussed multiple times on this site, but all the other topics seem to cover constant I/O latency, while the I/O problem we need to solve on our server occurs ...
- 51
3
votes
3
answers
1k
views
Is slow IO on my cloud server causing my slow server restart issues?
I'm running two servers on Rackspace cloud one for the web app and one for the db and redis instances. The web server has 1Gb of ram and single core. Nginx sits in front of unicorn which is running 2 ...
- 131
1
vote
2
answers
2k
views
High Iowait + High load average on a monitoring server
I've a nagios server which was perfectly working up to a few days ago. I've stopped it and restarted it to increase its RAM, and since then, iowait increased dramatically on the server (more than 20%, ...
- 115
1
vote
2
answers
251
views
CentOS 5 extremely slow when is running a download
When my server is downloading a file or executing other IO operations the other server functions become extremely slow (almost locked). Even other functions that do not use the network. When a ...
1
vote
0
answers
167
views
high linux server load
I have a problem with high server load (load average from 10 to 100+) when there is a lot of web traffic. There are also noticable delays when reading/writing files.
Machine is a Apache web server. ...
- 147
1
vote
1
answer
395
views
Why does md resync cause no iowait?
I've known the defintion of %iowait as
Time the CPU spent idling/blocking, because it had to wait on an IO operation to complete.
Now take a simple Linux system with an mdraid1 and two disks.
/...
- 168
1
vote
1
answer
98
views
What happened to hard disk
I suspect that with my hard drives is something wrong.
iostat -d -x -m
root@srv2:~# iostat -d -x -m
Linux 2.6.32-5-amd64 (srv2.host.com) 04/23/13 _x86_64_ (2 CPU)
Device: ...
- 285
2
votes
1
answer
784
views
Read IO Wait Increase
While troubleshooting a performance issue on a Debian Linux box running ext3 on software RAID 1 I redirected the output of a process writing useless temporary log files to /dev/null (ln -s /dev/null/ ...
- 181
1
vote
1
answer
3k
views
Copying cause big iowait
I have dedicated server with 3 HDD. System disk, backup disk (same as system disk) and data disk. When I copy lot of data with cp (say, between backup disk and data disk) load average goes sky high.
...
- 53
6
votes
4
answers
3k
views
What would cause IO Wait on a SAN?
I understand IO wait when I see it on a server, it means that the CPU is blocked while I wait for the IO to catch up [source].
I am trying to understand why a SAN stats would show a high IO wait - ...
- 2,186
2
votes
1
answer
2k
views
Debugging I/O issues on a linux server
What are some ways to debug I/O issues on a linux server?
I've been using:
# nohup top -b -d 10 > /var/log/top.log &
# nohup iotop -b -d 5 -o -t > /var/log/iotop.log &
PS: hardware is ...
- 6,681
1
vote
1
answer
661
views
How to manage iowait over cifs?
For backup purposes we have Cifs file Server running that contains encrypted containers for backing up the more sensitive data. The container is mounted with cryptsetup and loop as a local filesystem ...
- 23