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

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High disk I/O activity in CentOS server

I have about 16 websites in a CentOS dedicated, and I am having some problems on high traffic hours, it seems to be a high disk I/O activity causing a general slowdown. I've installed atop and this ...
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111 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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1answer
20 views

Finding CPU / IO time per process [closed]

I'm trying to find by my own why Wordpress is slow when running on a Raspberry Pi (I have some intuitions but I want to measure it). I'd like to find the time spent by a process waiting for IO, using ...
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31 views

DRBD high iowait every 65 seconds

I have a peculiar problem: simple INSERT queries to MySQL slow down and appear in my slow q logs every 65 seconds exactly. My stack looks like: mysql56u (IUS) on CentOS over ext4 over drbd over ...
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61 views

No Space left on device after Jenkins installation

Is there any reason i would get a 'No space left on device" error on mkdir. I have confirmed that i have enough space left. around 68% is free. and also i have 1% iNodes consumed. This is CentOS 7 ...
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Sustained io testing linux

I wish to hammer the io of some disks for an extended period of time and become aware whenever I can't read from a block (or some other symptom letting me know of an issue with backend storage). There ...
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1answer
23 views

Is “'Light-Speed' Disk Access” really a thing? [closed]

I just saw an advert for Hyve hosting on You Tube. One statement made me curious, they said they offer "'Light-Speed' Disk Access": Is this just a fancy way of saying they have optical technology, ...
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1answer
987 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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25 views

I/O and RAM limitations are important for Hadoop performance. But is disk speed related to I/O?

Hortonworks says this: "Most often performance of a Hadoop cluster will not be constrained by disk speed – I/O and RAM limitations will be more important." * How is disk speed not related to I/O ...
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40 views

Does Linux, Apache HTTPD or PHP cache frequently / recently accessed files?

Let's say we have a simple index.php file that goes: <?php inclde('file1.php'); inclde('file2.php'); inclde('file3.php'); Presumably, this will ultimately result in three additional ...
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1answer
24 views

High on %wa from top command, is there any way to constrain it?

Here's my last top info before it stucks: top - 18:26:10 up 238 days, 5:43, 3 users, load average: 1782.01, 1824.47, 1680.36 Tasks: 1938 total, 1 running, 1937 sleeping, 0 stopped, 0 zombie ...
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Virtual machines and I/O heavy workload, is it ever sane?

I have seen on numerous virtualization services (Azure) and products (vmware,kvm,hyperv) I/O and system stalls under heavy I/O workload. My questions are: Is it ever sane to use a Virtualized ...
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16 views

mdadm and LVM high load and IOwait

I've got a new CentOS 6.6 server with 2 HDD with mdadm & LVM. As I've used the CentOS install CD I assume everything should be aligned properly. I've just written a KVM image to a LVM LV using dd ...
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2answers
134 views

99% disk IO spikes with Percona

So we have a server that has seemingly random spikes in disk I/O, going up to 99.x% at random times and for no obvious reason, staying high for a while, and then going back down. This didn't use to be ...
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932 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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6answers
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I/O Performance Benchmarking Linux

Just finished setting up a poor mans SAN with iSCSI and want to benchmark it. What are some good I/O performance benchmarks for Linux besides: hdparm -tT /dev/sda1 How do I get a IOPS measurement? ...
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1answer
56 views

What it means when Linux has no I/O scheduler

I have some virtual machines running Ubuntu cloud-based image 14.04-1 LTS version. I wanted to see the IO performance of different IO schedulers on the VM so I went to ...
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32 views

PHP-FPM Stuck & High IO

Actually on my mutual hosting server I'm using PHP 5.6.3 with one pool. Sometimes, my php-fpm process is stuck with 50% of WA and I can't kill it, I can't even restart my VM. I'm using 245MB/3968MB, ...
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1answer
44 views

ubuntu kvm disk io slowdown after some tyme

Host system: Ubuntu Server x64 12.04 mdadm raid 1 (/dev/sda /dev/sdb) no lvm dd bs=1M count=256 if=/dev/zero of=filename conv=fdatasync avarage ~ 40 MB/s NCQ on disks is disabled WriteCache is ...
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46 views

MySQL slow file I/O

I got a little issue with MySQL having slow file IO. When benchmarking 1k blocks (I did them on purpose that small for worst-case) I get an hdd speed of about 2MB/s. When looking at iotop while ...
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2answers
42 views

how to find the highest IO consumer on a disk? [closed]

Can some one help to find highest IO consumer on each individual disks? i.e Which process consumes the most IO on /dev/sda, the highest IO consumer on /dev/sdb etc.
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File IO being slow

I've rented this root server with a RAID1 mdadm software raid setup. Using dd to benchmark the file IO speed it achieves 230MB/s write (default blocksize). Certain tasks such as mysql are way slower, ...
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2answers
33 views

how to check if a process with heavy io usage is running properly

I am now managing a computer cluster for scientific computing. Some processes in the cluster need heavy io usage. Now I find such a process: Its state changes rapidly between DOWN and RUN and its ...
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1answer
36 views

What is the purpose of a ramdisk when fadvise exists?

My understanding is that fadvise will tell the system that the indicated files should be stored in the file system cache (RAM). What is the purpose of mounting a directory in a ramdisk when you can ...
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Is there a way to delete 100GB file on Linux without thrashing IO / load?

I have a huge log file I need to delete on a production web server. I'm worried it'll bring the system to a crawl if I rm it on Linux. Any brilliant ideas? Update: Filesystem: ext3 Partition: /var ...
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1answer
36 views

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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3answers
463 views

Extremely High Hard Disk Reading Usage

My VPS configuration is as follows: H.D.D = 25GB RAM = 256MB OS : CentOS 5.5 I received an email from server provider showing that my VPS H.D.D read usage is 137GB in one day. I have installed ...
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5answers
653 views

Expected throughput when re-building RAID array?

I'm just doing some testing on a NAS RAID array we've been lent to see if we want to deploy it. Just to see whats what, I decided to see what kind of network performance we get when it's re-building a ...
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1answer
2k 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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using temporary files vs pipes advantages and disadvantages

Say I have a file named jobs.csv and I would like to get the top 50k jobs done by Foo I can either do: # cat jobs.csv | sort -u | head -n 50000 > /tmp/jobs.csv # cat /tmp/jobs.csv | while read ...
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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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Are networks now faster than disks?

This is a software design question I used to work on the following rule for speed cache memory > memory > disk > network With each step being 5-10 times the previous step (e.g. cache ...
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2answers
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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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5answers
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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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79 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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1answer
65 views

How to disable search body in dovecot?

We run mail server of 30k e-mail accounts (Maildir) with Dovecot imap server. We suffer from high IO load, especially when a user starts to search large IMAP folders. Is any way of preventing search ...
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Linux - How can I see what's waiting for disk IO

I have a server that has a really high load. Nothing is jumping out at me in terms of CPU usage, and it's not swapping. I think it's cause some processes are waiting for disk IO, and I want to see ...
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64 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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1answer
63 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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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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1answer
70 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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1answer
83 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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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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469 views

How to reduce I/O on EC2 micro instance running wordpress

I have been running a very small wordpress site on Amazon EC2 for about 2 months, using the free tier micro instance. I have been getting billed a few dollars each month for going over the disk I/O ...
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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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1answer
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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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47 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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1answer
174 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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100 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 ...