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

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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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Change Gluster default block size

I'm building a Gluster server, using Gluster 3.7 on top of Centos7. In the profiling report, read is always in the same 128k block size. And write can aggregate to bigger block size, thus have higher ...
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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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How to identify heavy write to disk?

I have this problem with server running CakePHP application. The server is insanely slow, I first thought that it's application problem, but then I found constant 5-6MB/s write to disk. What is the ...
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How can I monitor network I/O usage per process under Linux?

Such known tools like iftop/iptraf display network I/O per interface and per connection. Is there a way to see network I/O statistics per process?
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44 views

Bytes read / written SNMP value differs from iostat

I am trying to monitor my server over SNMP and UCD-DISKIO-MIB::diskIONRead.1 gives me 1344574464 while iostat reports 9701669 kB_read. Why the discrepancy? I don't have to mention that I am monitoring ...
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LXC (proxmox) JBD high (100%) IO utilisation

We have a dedicated server running a number of smaller guest VMs containing for example, HTTP server, MySQL and some real-time applications. However we find that JBD inside the guests are often ...
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22 views

Ubuntu hangs while running make test in IO Socket ssl

Hello I am running ubuntu 14.04 and perl version 5.23.9 (compiled) When I try to build the IO::Socket::SSL module , the machine always freezes. So I installed the module manually. Download from ...
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32 views

Serve 200 without reading the request

I have a system where Server receives large files from clients Files are unused and deleted immediately Clients cannot be updated to stop sending files There are a known number of clients (required ...
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2answers
69 views

Massive performance degradation on sustained sequential write

I'm in the process of migrating data into LUKS partitions. Now that the operating system drive is running off LUKS, I tried to start migrating the data drives. Then the server stopped responding. ...
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30 views

Gentoo virt-manager IO throttling

I have a problem with virt-manager (or qemu/libvirt) installed on gentoo. Here is My virt-manager installed on Debian Jessie: There I have IO throttling but not on my Gentoo: I tried to search ...
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Why does SSHFS I/O latency test much faster than local RAID & NFS?

SSHFS tests for server I/O latency using dd returns very surprising results, so much so that I'm worried this might be some problem either with the test method or configuration. Test 1 on local RAID ...
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Is there a way to get Cache Hit/Miss ratios for block devices in Linux?

Is it possible to see in Linux how many read and write requests from user space end up causing cache hits and misses for block devices?
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How to keep md-raid from blocking IO?

I run a server with md-raid (software) level 1 (2 HDDs mirroring) and several different applications run on it. The problem arises when file-intensive jobs (e.g. extracting large archives) run while ...
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1answer
21 views

Improving I/O rates for EBS snapshot backed volumes

I'm working with a system that takes a set of 42 rotating daily EBS snapshots of each of its numerous (40) volumes for disaster recovery purposes. EBS volumes are aggregated into a RAID volume. A set ...
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1answer
34 views

How can I determine which files have high I/O in Windows?

In trying to reduce the storage bottleneck on a Windows server (2008 R2) I need to find the files that have the highest I/O over a long period of time (aka 'hot' files) so I can move those to SSD ...
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2answers
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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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4answers
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figuring out high load cause from top and iotop

What should i do if I want to prevent this high load. My website becomes slow when load is higher than 8. Please see iotop result too. top - 20:23:10 up 127 days, 3:22, 1 user, load average: 9.92,...
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2answers
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Disk IO Rate: What causes it and what does it mean to me?

I just got a mail from Linode saying that my account "has exceeded the notification threshold (1000) for disk io rate by averaging 1017.36 for the last 2 hours. " My question is just out of curious: ...
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1answer
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monitoring disk i/o via wmi

I'm using WMI to monitor Windows Server 2003 and Windows Server 2008 hosts. I got all the info I wanted but the disk I/O performance. I've tried quering the "...
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1answer
64 views

Filesystem Performance for LUKS Encrypted Volumes?

As you can format a LUKS volume with any filesystem you want, are certain filesystems better-suited to IO performance against an encrypted filesystem? Specifically, I'm wondering about a loop device ...
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4answers
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Measuring 'total bytes written' under Linux

We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article ...
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What are front merges in I/O scheduling and how can I tune this parameter?

My Linux uses the Deadline algorithm for I/O scheduling. One of the parameters is the front_merges parameter under /sys/block/sda/queue/iosched/front_merges. By default it is set to 1, which means ...
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2answers
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monitor IO to tmpfs partition?

How can I monitor the write speed to a tmpfs partition. It does not appear in the output of vmstat or iostat. I am running several python processes that are writing heavily to tmpfs and contributing ...
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1answer
49 views

Check If I/O causing high load average

I wants to understand how to measure if I/O is causing load average high and how to calculate optimal and critical I/O value. Because sometime there is a load spike on my server but other ...
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How I can reduce disk IO in MySQL 5.6.26?

I was using MySQL version 5.1.52 for my application but recently I have updated it to 5.6.26, but now I am facing very high disk IO. Following are system configuration: OS : Linux 2.6.39.4 RAM : ...
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55 views

How to find the bottleneck for slow rsync

I want to find the bottleneck for a slow rsync. I see these parts (on byte flow order): IO on source CPU on source Network CPU on destination IO on destination How can I debug this?
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Acceptable I/O speeds for 6 x 250GB SSDs in RAID 10

I'm running CentOS 7 (XFS filesystem) on a dell server with a PERC H700 raid controller. Inside this server I have 6 x Samsung 850 Evo 250GB SSDs (yes they are consumer drives however, this is a home ...
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141 views

KVM bad IO sync performance in Linux guest

I'm setting up virtualized Ubuntu 15.10 guest inside Ubuntu 15.04 server using libvirt and KVM. Storage in host system: # mount | grep ext4 /dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,...
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collectl vs strace - reported block io read/write size

I've got an xfs mount with standard settings (it's an AWS host): [root@host ~]# xfs_info /dev/xvda1 meta-data=/dev/xvda1 isize=256 agcount=4, agsize=524224 blks = ...
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18 views

Long Response Times for Reads via FCoE

We're getting some intriguing performance with our new FCoE environment, and I was hoping that people could let me know if what we're seeing is expected behaviour. Our switching environment consists ...
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How can I debug: iostat shows 100 util but there's 0 read or write in iotop

The server is an AWS EC2 instance. Ubuntu 14.04.2 LTS. I have an EBS (xvdf is the device name) mounted to the instance. And this is the problem drive. From iostat I see that drive is 100% utilized (...
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How to check what is causing performance issue

[Edit] This question is different than what is suggested by the moderator, I am trying to find out what could have caused the API to become slow because of the few lines of codes. I am not trying to ...
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How to ensure that I/O requests have returned to a normal rate?

On Amazon Web Services I am using a t2.small EC2 instance as a VPS serving a few websites on a LAMP (PHP) stack. I was just hit with a bill which almost triples my usual bill. I see that my I/O ...
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Starting PHP session sometimes take very long time

Sometime ago we have came upon interesting problem. Sometime (not everytime, lets pretend nearly each 100-200 hit) session_start() takes very long time. Up to 60 seconds. (longest one was 63, ...
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How many milliseconds of await is considered to be high? [closed]

How many milliseconds of await is considered to be high? i have 800ms and 600ms iostat -x avg-cpu: %user %nice %system %iowait %steal %idle 1.28 0.00 0.22 0.90 0.00 ...
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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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Get NewRelic to respect ionice'd processes

On our web server, we perform an incremental backup of our files every 4 hours using rsnapshot. To perform the actual copying of files, I've configured it to use a custom script, cp-nice that has the ...
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Most side effect-free way to archive a large file while it is being modified

I am looking after an application that generates a large amount of data in a log file (about 5G a day) on a Red Hat server. This process runs for 24 hours during the week, so there is no point in the ...
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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
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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 non-...
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1answer
58 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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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
43 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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7answers
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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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370 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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__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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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 ...