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

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Redis parent process smashing disk despite appendfsync = no

We are seeing loads of IO from redis-server despite our save operations being set to occur once every 15 minutes only. The workload is a "full page cache"; we store blobs of compressed HTML. The HTML ...
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4answers
537 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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1answer
28 views

Ubuntu 12.04 high io by root process

Ubuntu server 12.04. Installed on hdd disk. There is postgresql database on server runing on other ssd disk. The problem is in high io by some root process on hdd disk. iotop shows 2 processes with ...
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Disk i/o latency using file system [closed]

How to calculate Disk read and write latency in Linux. Is it possible, to do the calculation using /proc/diskstats or /sys/block/*/stat file system. if it is possible Please tell me how to ...
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1k 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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Ubuntu CPU I/O Rate Spike

Getting really crazy spikes today on a Ubuntu server for CPU / IO. CPU Chart is showing as much as 210% CPU usage - no idea how that is possible. IO has gone as high as 11912. (Usually well under ...
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1answer
24 views

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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Can anyone explain precisely what IOWait is?

As much as I have read about iowait, it is still mystery to me. I know it's the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also ...
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38 views

Finding correct IOPS to set limit with ESXi 5.5u2 and vSphere

We're running an ESXi 5.5u2 hypervisor that has a mirror of 2 15k SAS drives with a couple of VMs inside and we noticed some services become briefly unreachable if another VM is using all the IO. So ...
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108 views

__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
885 views

Direct I/O on Linux

I'm trying to enable Direct I/O on /opt (/dev/sda6, ext4) on Linux Mint 13. What I'm trying is: mount -o dio,rw /dev/sda6 /opt as root. The system responds with: mount: wrong fs type, bad option, ...
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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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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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52 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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2answers
136 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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1answer
24 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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2answers
43 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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64 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
31 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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3answers
2k views

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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38 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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166 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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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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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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69 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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66 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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53 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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56 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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44 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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48 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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48 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
40 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
483 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
654 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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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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13answers
18k views

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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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
562 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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92 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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73 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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80 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
85 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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2answers
61 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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1answer
99 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 ...