IO (or I/O) is an abbreviation for input/output, most commonly referring to disk input/output.

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Does AWS EC2 have secondary disks scattered across the cluster?

I am using AWS EC2 Linux m3.xlarge to run a program called "Smart Information Retrieval System" which performs many I/O operations to/from the disk. I have tried running the same program on my laptop ...
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Why CPU spent time on IO(wa)?

I know wa (in top) measures the CPU time on waiting for I/O. Many articles say that. But I am confused that, based on 2 knowledge points: if a process uses a system call to read disk, the process ...
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Benchmarking for DISK I/O Writes Per Second - ElasticSearch and MySQL

During working on our project we needed to decide should we use "ElasticSearch" or "MySQL" to record the audit/trail logs of the system. Searching speed is not an issue here, we needed to see the disk ...
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2answers
38 views

how do I know if an SSD reaches its performance capability?

I was monitoring a new db server with SSD RAID-10 installed. It works fine for now but I was worrying someday it could reach its capability as the business goes on. So how can I know that before it's ...
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55 views

Restrict I/O Write usage using cgroups

I am trying to restrict I/O write usage on my server using cgroups. Here is my partition table info: major minor #blocks name 8 0 10485760 sda 8 1 9437184 sda1 8 ...
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226 views

High load due to I/O wait in Ubuntu 12.04 on EC2 instance

I am using Ubuntu server 12.04 , having trouble finding cause of load, I have seen change in response time of server from past week after reading Linux Troubleshooting, Part I: High Load It seems ...
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52 views

6 GB/s SAS RAID 10 (6 Drive) vs. 3 GB/s SAS RAID 10 (14 Drive)

I am running MS SQL 2014 Standard and have a Dell MD 3000i iSCSI SAN. Rough specs: Dell R610 With PERC H700 controlling 6 x 2.5" 15K SAS drives (6 GB/s) Dell MD3000i with 14 x 3.5" 15K SAS drives ...
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39 views

How to find reason for hanging process (probably I/O related)

on Ubuntu 14.04 when I open a file browser or an "Open File" Dialog, the application hangs for about 5 to 10 seconds. I suspect this is due to some NFS requests. But how can I find out for sure? Is ...
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52 views

Disk I/O at limit with software raid

whenever I use rm or cp on a bigger file structure the disk i/o is going up to the top, but not with the focus on cp or rm, it is the software raid sync. My knowledge in this area is limited. The ...
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43 views

interpreting disk stats using sar

I have JBOD and Cassandra installed on it. I'm trying to figure out if my disk are totally free or they are boring. The sar -d result is in the end. As I understand until %util is low (less then 1) it ...
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42 views

How efficient is the tac command on large files

The taccommand (catreversed) can be used to read a file backwards, just like cat reads it rom the beginning. I wonder, how efficient this is. Does it have to read the whole file from the beginning and ...
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37 views

MongoDB hogging IO but it doesn't show in mongotop or mongostat

Iotop says mongod is using a lot of IO (96.32%) for a long while but mongotop and mongostat show a bunch of zeros. How can I better monitor mongodb and find out what's happening?
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36 views

IO Rate is exceedingly incrementing

I have read through Is a 'high' IO rate healthy?, and was at ease when I read someone say that even 50,000 / hr wasn't an issue.... or not unhealthy, to answer their question; so I increased ...
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60 views

IO tasks easily starve eachother on 3Ware 9650SE

I have a server (Debian 6 LTS) with a 3Ware 9650 SE RAID controller. There are two arrays, one RAID1, one RAID6. It runs Xen 4.0, with about 18 DomUs. The problem is that I experience that IO tasks ...
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470 views

kworker consuming +90% IO and zero disk write

this is a standard apache web server on AWS Linux AMI + EBS. We are noticing high load average (+8) and iotop -a shows: Total DISK READ: 0.00 B/s | Total DISK WRITE: 2.37 M/s TID PRIO USER ...
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43 views

Can poor Internet connection affect the IO read on my server?

I'm trying to spot the culprit causing too much IO read in my server. Issuing IOTOP -ao I have come accross many httpd processes among which one caught my attention: PRIO USER DISK READ ...
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61 views

How can I monitor disk IO load on a Windows 2008 server?

We are running multiple processes on our servers, which are mostly CPU intensive, but also use the local HDDs for reading the data. I can trivially look at the CPU load and memory usage in TaskManager ...
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74 views

Windows Server 2012 with SSD local drives — Random or Sequential I/O?

How can I determine where my Windows Server 2012 is using Random or Sequential I/O operations when writing/reading the local SSD storage? I have been asked to provide details to our hardware vendor ...
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77 views

gstat output on FreeBSD: does it show an average over time?

When you run the gstat command on FreeBSD to get information about i/o performance, you can pass the -I (interval) option to change the default interval from 1 sec to some other time frame. My ...
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1answer
56 views

How to save iotop's output for a specific period of time

I am trying to discern what processes are making huge Read/Writes on my server disk. I know I can use iotop -ao but is there a way I can save iotop's output for a specific period of time to study ...
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2answers
45 views

What is the difference between truss -D and truss -E?

I am currently analyzing a command on Solaris that reads from a file and has very low performance. The truss -D commands shows me read system calls taking up to 0.03 seconds, but when I use truss -E, ...
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371 views

Evaluating the CPU I/O wait on Linux

Doing a top to check the io wait, I get these figures: Cpu(s): 6.7%us, 1.4%sy, 1.2%ni, 85.5%id, 5.0%wa, 0.0%hi, 0.3%si, 0.0%st Looking at these figures (%us ~= %wa), do they mean that: ...
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50 views

VPS Unknown Read/Write [closed]

I had an lfd email alert - I have installed CSF - today revealing that my server (Centos 6.6) has been using a lot of server resources for 5 minutes. I checked my VPS graphs and noticed that my ...
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65 views

how to find cause of io spike

Everyday at around the same time, the IO usage on the server where our mysql slave goes up to 100%. I have setup a script that takes IO information every five minutes so I can find out why this ...
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“Nosy Neighbor” and the CFQ scheduler

I'm trying to understand how does using CFQ affects the "Nosy Neighbor" problem. I'll ask it a bit naively, can a "Nosy Neighbor" even exist when using CFQ? Isn't that CFQ should make sure all ...
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123 views

Beyond 1Gb upload on a single linux server

I have a high hit nginx web server on CentOS that provides static large content. when the number concurrent connection are low, server could easily provide up to 4Gb of traffic , but when the number ...
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1answer
193 views

Does changing /sys/block/sda/queue settings take effect immediately?

How long does it take for changes to the following settings to take effect: /sys/block/sda/queue/scheduler /sys/block/sda/queue/rotational /sys/block/sda/queue/read_ahead_kb Is it ...
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348 views

Innodb performs IO Operation when idle

I am currently doing some stress testing where I am pushing inserts to the database as fast as I can. The simulation inserts 10000 records per second. After inserting around 200 million records I ...
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157 views

rrdgraph generation fails on high IO load

We have a 4 core CPU production system which does a lot of cronjobs , having constant proc queue and an usual load of ~1.5. During night time we do some IO intensive stuff with postgres. We generate ...
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424 views

BUG: soft lockup - CPU#0 stuck for 23s! on XEN PV debian related to high i/o load

i am currently experiencing some problems with my Debian Xen System. It runns on an old opteron System with two Dual Core AMD Opteron(tm) Processor 275 CPUs. I am using image files (block devices) ...
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184 views

Unreasonable performance expectations for RAID 0 performance?

This is my first time building a machine with a hardware RAID card. We bought a Dell T620 with the H710P RAID controller (1GB NV Cache), a 160GB Solid State Drive (SATA Read Intensive MLC 3Gbps), and ...
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846 views

Changing the I/O scheduler for a specific disk

I would like to change permanently the I/O scheduler for a specific disk on Fedora 20. According to what I have found, this can be achieved by executing the following shell line as root: echo ...
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832 views

Linux - KVM - very slow disk io

The I/O performance of my new server is pretty low. I Googled and tried everything I can imagine. First of all, here are the Hardware Components: AMD Opteron(tm) Processor 6344 4x Seagate ...
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390 views

Is it possible to configure the Linux kernel I/O scheduler for an NFS mount?

On a normal block device you can change the i/o scheduler like this: # cat /sys/block/hda/queue/scheduler noop anticipatory deadline [cfq] # echo anticipatory > /sys/block/hda/queue/scheduler # ...
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325 views

Mongodump on Gridfs is killing the host IOs

I'm trying to make a mongodump from our production mongodb while the production is running. We have three production instances, one regular mongodb, one with very few gb of data on gridfs, one with a ...
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480 views

Linux page cache slows down IO on dual cpu server with 64GB ram

I have a massive problem with the linux page cache which slows down the IO. For instance if I copy a lvm partition with dd, linux cache the data in the buffers or caches (free –m). That is not the ...
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450 views

Azure IO performance

We have a number of Windows Server virtual machines that we use for .NET and Java development and QA. I find Azure attractive for the obvious reasons but mainly for the opportunity to reduce ...
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158 views

How can I measure complex I/O activity to develop realistic benchmarking? [closed]

I need to retrieve a few metric from my service server to benchmark another stroage solution. There are various options are provied by benchmark program(I choosed ...
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160 views

can Iowait cause significant RAM consumption increase

I have a node.js process running continuously on a linux EC2 instance, it extracts data and stores it in mysql. Some reads are also performed on the database. The process can run well during hours or ...
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1k views

htcacheclean doesn't seem to be cleaning the cache

I'm running mod_cache with apache 2 on a fairly high traffic'd site. I've set the htcacheclean to run in demon mode every 10 minutes to keep the cache at 4GB. It's currently at 15GB and doesn't seem ...
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415 views

Setting I/O scheduler for SSD based RAID array on EC2 instances

I created a RAID array using the 2 local SSD drives on a EC2 c3.4xlarge instance. # mdadm --create /dev/md127 --level=0 --raid-devices=2 /dev/xvdf /dev/xvdg # mkfs.ext4 /dev/md127 # mkdir /data # ...
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__ticket_spinlock high cpu

We are having a strange problem on our Ubuntu 10.04 KVM infrastructure, where periodically, one of two vm webservers freaks out, with persistently high load, even if we restart the applications. (the ...
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1answer
492 views

What dose these units means in zabbix?

When i try to set some items for my disk read and write, I found it by vfs.dev.read and vfs.dev.writefor zabbix-agent. This item contain a parameter named type which some of them are unknown for me. ...
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103 views

server hangs randomly without log entries

My physical server hangs randomly and I do not get any log entries during that time. So I let a script run: while true; do date >>/tmp/dates; sleep 1; done & disown After some minutes the ...
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762 views

report per-process IO stats with pidstat or sar

I'm trying to track io usage of a few "suspect" processes over time. Ideally would like to make those stats available via munin, or push directly to graphite. However, as a starting point it would be ...
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386 views

IOMeter showing hardly any data

I ran IOmeter on a Windows Server 2008 R2 SP1 server for 18 hours and when I clicked on "Stop current Test and Save Results" it stopped the worker processes (I only had 1). When looking at the ...
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93 views

Does ESX 5.X cache guest IO?

I am trying to find out if guest can see successful disk flush operation, but the host doesn't actually flush it to disk? How does ESXi work with guest I/O? Are they cached by ESXi before being ...
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169 views

How to benchmark maxCache 3.0 with SSDs? [duplicate]

We're a software development company and previously outsourced the HW side of business but now we're looking into building our own private cloud. We recently purchased a few servers, one of which is ...
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510 views

Why are pgpgin/s and majflt/s inconsistent in sar -B?

In sar -B ouptut, I would naively expect pgpgin/s to equal majflt/s multiplied by the system page size. From man sar: pgpgin/s Total number of kilobytes the system paged in ...
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326 views

Finding root cause of 99.99% iowait with 0% SWAPON

Users and DBAs are complaining that "Oracle is slow" on our OEL servers. The only thing I have found from the OS standpoint is that there are some strange IOWAIT stats from iotop. Output from iotop: ...