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

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Reason for high CPU time when executing fio

After weeks of troubleshooting some performance issues I have on my VPS running Ubuntu 12.04 LTS, I am getting closer to the conclusion that the problem is related to IO. When I have a considerable ...
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104 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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167 views

HDD operations slow server down, hangs completely

When running a tar cvzf command or copying large folders on the production server, the CPU load goes up to 8.5 (running on 8 cores) and the whole system hangs, neither apache is responding to any ...
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Limit copy speed

Unfortunately we have a pretty bad HDD performance on one of our servers and as soon as we start bigger copy process it stops to deliver any Apache response, which is really bad. Is there a way to ...
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Disk performance below expectations

this is a follow-up to a previous question that I asked (Two servers with inconsistent disk speed). I have a PowerEdge R510 server with a PERC H700 integrated RAID controller (call this Server B) ...
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109 views

low priority linux filesystem

Does anybody know of a some sort of (virtual) filesystem that will run as a low priority i.e. All other regular disk activity will take priority? The reason for this is an application I am developing ...
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Input/output error reading USB backup drive on CentOS 6.4

I'm suddenly seeing some strange behaviour on our USB backup drive that doesn't make sense to me: (2013-10-21 14:58:23 [root@newdc /]$ cd /mnt/backup/ (2013-10-21 14:59:03 [root@newdc backup]$ ls -la ...
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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 ...
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How to keep subtree removal (`rm -rf`) from starving other processes for Disk I/O?

We have a very large (multi-GB) Nginx cache directory for a busy site, which we occasionally need to clear all at once. I've solved this in the past by moving the cache folder to a new path, making a ...
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1k 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 iowait for unknown reason

I'm having a hard time figure out the reason cause high iowait on my server. This is log of iostat -xm 5 5 Linux 2.6.32-358.6.1.el6.x86_64 (prod-1.localdomain) 09/28/2013 _x86_64_ (16 CPU) ...
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806 views

High disk usage in CSRSS.EXE

I recently started working on the server for a certain software (Tango). The users complained that it recently became extremely low, so I used an application (ProcessHacker) to see the resource usage ...
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101 views

Two servers with inconsistent disk speed

I have two servers of identical spec (bought at the same time), except for the drive configuration: Server A: C: and D: drives are partitions on the same 2 disk RAID 1 E: is a 2 disk RAID 0 ...
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37 views

IO impact with symlinks

I have an NFS mount for web servers, I've moved log files to local storage to minimize IO load on NFS server but I've created symlinks for these logs (NFS share -> local storage). Is this still has ...
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2answers
389 views

How to maximize I/O on an OpenVZ VPS node?

I have an OVZ node with 46 VPSes. The SSD drive had 400Mb/s but after filling the node with VPSes the SSD drive sometimes drops to 40Mb/s. How can I prevent this from happening? Is there a way to ...
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1answer
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Apache2-server append a string to a JavaScript file before client receives the file

I never touched the Apache 'inner files', but now I need to add a string (that isn't static) to the end of some JavaScript files when serving them via Apache. What should I do / learn to achieve this? ...
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104 views

File I/O Throughput

I have an IBM x3650 M4 server (64-bit) running Ubuntu 13.04 Desktop (32-bit). I realize that this is a non-standard setup by it's being driven by other requirements. I am seeing slow file writes ...
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linux: how to simulate hard disk latency? I want to increase iowait value without using a cpu power

Is it possible to set an arbitrary delay for I/O operations? I would like to learn how do iowait and disk %util impact the performance. There are a lot of tools to stress the disk (bonnie++ etc.) but ...
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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 ...
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503 views

Dramatic disk I/O performance difference for two disks on same machine

A small machine (1 core, 1 GB RAM, CentOs 6.3) virtualized via Citrix Xen has 3 virtual disks with very different sizes. > cat /etc/fstab (snippet) ... /dev/mapper/vg_stagingnfs-lv_root / ext4 ...
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How do limit disc i/o during backup?

I have a cron that basically do a simple "tar zcf" in the night. The server has: 8 Cores - Intel(R) Xeon(R) CPU E5606 @ 2.13GHz 25GB RAM Ubuntu 12.04.2 LTS Hardware RAID 1 (LSI Logic / Symbios ...
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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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49 views

File transfer slows down the server response

We are on Win server 2003 and we transfer the files across the same intranet either using CuteFTP or through mapped drives. The problem here is the file transfers start fast and get slower as time ...
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329 views

Why is my synchronized I/O so bad compared to direct?

I have two 3TB disks in a software RAID 1 setup and the host OS is 64bit Debian wheezy. Issuing: dd if=/dev/zero of=test bs=64k count=3k oflag=direct && rm test Yields: 201326592 bytes ...
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High await in sar

My database server has the following sar output for the data device: [postgres@dbsrv07 ~]$ LC_ALL=POSIX sar -d |egrep "await|dev253-2" 00:00:01 DEV tps rd_sec/s wr_sec/s avgrq-sz ...
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debian Read-only file system error

I logged on to my debian box and tried running some commands and I was presented with the following message. sudo: Can't open /var/lib/sudo/username/0: Read-only file system After doing some ...
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393 views

VMWare ESXi: to extend a partition or create a new drive?

Is it better to extend an existing partition or to create a new drive in a VMWare ESXi virtual machine? I'll be using LVM to put the drive in an existing volume group on my VM and to extend a SAN ...
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532 views

High cancelled_write_bytes, high IO load, concurrent memory-mapping

I have a software for persisting/retrieving data from files (a bit like database, but it's not exactly a database engine). It's not open source and the documentation is sparse, therefore I don't have ...
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Windows server 2008 I/O counters

For an I/O capacity study I'm working on, (on a windows server 2008R2 system) I'd like to gather absolute I/O counts for a given physical (or logical) disk over a specific period of time. When I look ...
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286 views

Strange IO issue with Ubuntu 12.04

I have a very strange IO issue with Ubuntu 12.04 and MySQL. Currently the machine is only a replicated slave with an occasional read query hitting it. The disk utilization spikes randomly and ...
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Running a process within a limited amount of resources, in Linux

Is there a way to run a process (e.g. ls, du, find .. etc) within a strictly limited amount of resources (i.e. cpu, memory, I/O) aside from using nice & ionice, as I didn't find them effective ...
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whats the difference between 1lane and 2lane with SATA-3 speeds? [closed]

I read the beauty of PCIe is that a designer can combine two, four, eight or sixteen of PCIe lanes into a single data port. 2.5 Gb/s PCIe×1 5 Gb/s PCIe×2 I have two sata 3 drives that I want to ...
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iotop does not show writes

What could be writing on the disk that iotop does not show? # iotop -a Total DISK READ: 8.19 M/s | Total ****DISK WRITE: 3.34 M/s**** TID PRIO USER DISK READ DISK WRITE> SWAPIN IO ...
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Detect file update from modification time

Is there a way to see how often a file is being updated? I mean I need to see if the modification time of a file is updated in a dynamic way (same as tail shows if the file is updated in a dynamic ...
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572 views

Why is autovacuum using so much IO when running on a partition's master table after upgrading PosgreSQL from 8.4 to 9.1?

We have an application where we are collecting timestamp-based data. Since a month of data goes over 30M rows (and growing each month), we decided to partition the data on an year-and-month basis. We ...
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Flush-0:n processes causing massive bottleneck

I have a LAMP cluster that shares files via NFS and occasionally one of them will be stricken for a while when mysterious flush processes start appearing. Can anyone help me? The only way to resolve ...
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High load cause? [duplicate]

Possible Duplicate: what is my server high load cause (4 cores and 8 thread cpu) What is my high load cause? CPU,RAM or IO? 4 Core, 8 thread cpu top - 22:27:07 up 149 days, 5:26, 1 ...
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Poor guest I/O performance KVM Ubuntu 12.04

I have a guest VM running inside a 12.04 Ubuntu host. VM was created using the vmbuilder python script. On the host the phoronix-test-suite "aio-stress" gives a performance speed of >1600MB/s Random ...
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1answer
556 views

Limited I/O Performance in Dell T410

We have a small number of Dell T410 and T710 systems. Each has a Dell SAS 6iR controller with 6 SATAII disks, 1x160GB OS and 5x3TB DATA disks. We have been having disk access speed issues all ...
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548 views

Poor KVM guest IO performances

I've a DOM0 packed with two 3TB hard drives configured as a software RAID1, also sporting 16GB of memory. The DOM0's Linux distro is a CentOS 6.3 and the hypervisor is a libvirt-managed KVM. I'm ...
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jbd2/dm-0-8 consuming all I/O

What is jbd2/dm-0-8 and why It is consuming all my I/O usage and causing I/O wait? Is there anyway to disable this? Bonnie++ results: http://pastebin.com/iQCWP1qp $ sudo hdparm -t /dev/sda1 ...
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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: ...
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1answer
878 views

Identify which process is responsible for heavy disk i/o under FreeBSD

I wonder how I can monitor which process takes out all my IO bandwith. The only command i know is gstat but it shows cumulative info. Is there any tools i can use to inspect the running processes for ...
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Disk write speed much slower than read speed

I have a VPS server (WiredTree), running CentOS. After experiencing some performance issues I created a simple benchmark for disk read/write speed using the following script: echo Write to disk dd ...
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330 views

Linux buffer memory always stays at zero

One of my hosted server is a Xen guest running Debian and linux kernel 2.6.32 then 2.6.38. It has been running fine for quite some time (more than a year) but I recently noticed something weird. For ...
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Reduce the I/O priority of Windows Backup (Windows Server 2008 R2)

I have a PostgreSQL running on Windows Server 2008 R2 x64 box. And I have scheduled a backup everyday from the RAID 1 DB disk to a dedicated standalone disk. They are SAS 15k on Dell PERC 6i. I am ...
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Determining cause of high NFS/IO utilization without iotop

I have a server that is doing an NFSv4 export for user's home directories. There are roughly 25 users (mostly developers/analysts) and about 40 servers mounting the home directory export. ...
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732 views

Quantifying the effects of partition mis-alignment

I'm experiencing some significant performance issues on an NFS server. I've been reading up a bit on partition alignment, and I think I have my partitions mis-aligned. I can't find anything that ...
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5k views

Issues with Server 2012 using DFSR running on Hyper-V 2012

We have a number of Server 2012 systems, all of which run virtualised on Hyper-V 2012 server. We are having problems with two such virtual instances, both of which are used as file servers, whereby ...
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3k views

Strange high CPU I/O wait on postgresql server

I'm really struggling with a performance issue currently, where all my database queries takes up to a 1000 times more than normally, when my database server is under "heavy" load. I have a server ...