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

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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: ...
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279 views

How can I see which devices are used by a process?

iotop and iostat are great tools to see how much I/O is happening. But I haven't found out how these (or other) tools can show me the I/O rate per device and per process. So I'm looking for a way to ...
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Visualizing IO other then seekwatcher

Is there any other programs that can generate visuals/graphs/diagrams (movie and pictures) to visualize IO across a full device other then seekwatcher? NOTE: seekwatcher generates visuals(pic/movie) ...
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2answers
369 views

Simulate database I/O behaviour [closed]

I'm investigating some performance issue and I need a tool that can mock the same I/O behavior that a typical RDBMS is usually creating. I don't want to install a full blown RDBMS and mess around with ...
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1answer
497 views

I/O priority per LVM volume (cgroups)

How can I prioritize LVM volumes I/O performance using cgroups? I know I can use ionice to make changes at the process level but I wish to be able to do this per LV and not per process.
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306 views

how to do I/O sniffing

For sizing purposes I need to understand what requirements an application has to the I/O subsystem. I would love to do what I call I/O sniffing and obtain a list of events from the block layer like ...
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2answers
579 views

High Disk I/O on server reboot

A CentOS 5.8 machine has high Disk I/O upon starting up. The processes taking up disk IO are kmirrord, kjournald and pdflush. I have done the performed the following: 1) Mounted the filesystem with ...
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149 views

Munin graph Disk IOs for /dev/sda k unit interpretation

From Munin diskstats plugin Disk IOs for /dev/sda graph shows Max IO/sec -read/+write 1.75k/920.92. What does the k unit in Disk IOs graph mean?
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336 views

IO related performance bottleneck on a LAMP server

I am administering a big LAMP server with some thousand users. About a week ago, things slowed down, and the only thing I see that the IO latency is increased dramatically. Users experience slow page ...
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1k views

How to calculate the required EBS PIOPS for our mongo server?

We want to use provisioned IOPS EBS volume on our mongo machines, I'm a bit confused on how to calculate the number of provisioned IOPS to use. Currently we're getting an average of 25 IOPS (read + ...
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3k views

How to monitor NFS load from userland?

Apologies if I'm not using the proper jargon (although I'm a longtime linux user, I'm not an admin) or if this is a FAQ (though searching SE got lots of hits, I didn't see anything quite like this ...
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416 views

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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1answer
108 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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4answers
81 views

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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4k views

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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111 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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3k views

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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933 views

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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2k 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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840 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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103 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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39 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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407 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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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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106 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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185 views

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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544 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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604 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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50 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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365 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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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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552 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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446 views

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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1answer
566 views

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 way)...
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645 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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63 views

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 user, ...
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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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606 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 along, ...