Questions tagged [iowait]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
1answer
55 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 ...
2
votes
3answers
226 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 ...
0
votes
1answer
95 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 ...
0
votes
1answer
202 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 ...
3
votes
4answers
444 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
1answer
217 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 ...
1
vote
0answers
381 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 &...
0
votes
0answers
20 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 ...
1
vote
0answers
381 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 ...
0
votes
1answer
322 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 ...
-1
votes
1answer
2k 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 ...
0
votes
0answers
599 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 ...
1
vote
0answers
880 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, ...
4
votes
2answers
217 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 ...
2
votes
2answers
2k 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
vote
3answers
5k 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 ...
7
votes
1answer
15k 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 ...
20
votes
1answer
2k 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] ...
0
votes
0answers
865 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 ...
-2
votes
1answer
577 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 ...
2
votes
2answers
209 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.] ...
1
vote
1answer
923 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,...
0
votes
2answers
339 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,...
0
votes
2answers
853 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 ...
3
votes
1answer
9k 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; ...
0
votes
1answer
517 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 ...
0
votes
1answer
663 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-...
9
votes
1answer
12k 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 ...
0
votes
1answer
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 (mockbuild@builder17.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-52)) #1 SMP Tue Dec 4 17:43:34 EST 2012 ...
5
votes
2answers
3k 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 ...
3
votes
3answers
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 ...
1
vote
2answers
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%, ...
1
vote
2answers
221 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
0answers
157 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. ...
1
vote
1answer
302 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. /...
1
vote
1answer
90 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: ...
2
votes
1answer
548 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/ ...
1
vote
1answer
2k 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. ...
6
votes
4answers
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
votes
1answer
939 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 ...
1
vote
1answer
516 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 ...
2
votes
1answer
1k views

no disk io but iowait very high

there is no disk io going results of iotop Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO< COMMAND 1 be/4 root 0.00 ...
0
votes
2answers
1k views

Why load increase ,ssd iops increase but cpu iowait decrease?

There is a strange thing on my server which has a mysql running on it. The QPS is more than 4000 but TPS is less than 20. The server load is more than 80 and cpu usr is more than 86% but iowait is ...
8
votes
1answer
2k views

high load average, high wait, dmesg raid error messages (debian nfs server)

Debian 6 on HP proliant (2 CPU) with raid (2*1.5T RAID1 + 2*2T RAID1 joined RAID0 to make 3.5T) running mainly nfs & imapd (plus samba for windows share & local www for previewing web pages); ...
1
vote
0answers
322 views

Why does nginx 1.0.0 appear to not use the kernels open file cache on Gentoo? (high iowait)

free -m total used free shared buffers cached Mem: 7996 2043 5952 0 73 140 -/+ buffers/cache: 1830 6165 ...
2
votes
1answer
700 views

IOwait peaks blocks the whole server for 1-3 minutes

On my Debian VPS, I am getting peaks of IO wait, which blocks my server for a few minutes. On the screenshot, you can see the Idle (green) which suddenly drops for IOwait (pink), which eventually ...
7
votes
4answers
10k views

What is causing the unusual high load average?

I noticed on Tuesday night of last week, the load average went up sharply and it seemed abnormal since the traffic is small. Usually, the numbers usually average around .40 or lower and my server ...
2
votes
1answer
1k views

IO-intensive processes hang with iowait, but no activity going on

I have a bunch of IO-intensive jobs, and to boost performance, I just installed two SSDs in a compute server, one as a scratch file system, one as swap. After running for some time, all my processes ...
3
votes
1answer
1k views

How can i view the disk latency of a ZFS pool, or of the disks in it?

I'm using FreeBSD. I would like to write a munin plugin to log it, but i don't understand how to get this data.
2
votes
1answer
2k views

How to combine different pidstat outputs (CPU, I/O, Disk Usage)

I would like to use pidstat to get both -u, -r and -d flags. Is there a way to do so? The idea, is to get both CPU, I/O and disk usage. Cheers Ps. Combining the flags as -urd doesn't work in Ubuntu ...