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

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I/O and CPU differences between dedicated hosting and Amazon EC2

I'm looking to run a high population Minecraft server (150+ players online at a time). For those unfamiliar with the Minecraft server, it is a (non-multithreaded) application written in Java (some ...
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What creates CPU I/O wait but no disk operations?

I have CPU I/O wait steady around 50%, but when I run iostat 1 it shows little to no disk activity. What causes wait without iops? NOTE: There no NFS or FUSE filesystems here, but it is using Xen ...
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I/O Xen Server on disk filesystem ext4

I have a Xen Server 6.0 and one disk (2TB) report I/O error my vm is Centos 6.2 (filesystem ext4) end_request: I/O error, dev xvdc, sector 896084224 end_request: I/O error, dev xvdc, sector 896084312 ...
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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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160 views

Sendmail greatly increases value of Total DISK WRITE

Sendmail is installed on the server. It sends an average of 6 emails at 3K per second and writes 18 files in /var/spool/mqueue-client. Because of this high disk writes iotop: Total DISK WRITE: ...
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243 views

How can I determine the specific file referenced by fs_usage, which is listed by block

I was investigating a problem on a Mac OS X 10.6.8 Server, where users were complaining of access slowdowns. Network throughput slowed to a crawl. It felt like the server was overburdened. System ...
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Detecting Disk Writes Linux

my webserver running centos 5.7 is showing quite a lot of disk write activity which I cannot explain really. I run a few websites on this server with the help of nginx and php-fpm and xcache. On the ...
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IOs reads writes per file

My target is to equally separate mysql database across the number of drives, using symbolic links on tables. Now I can not seem to find the way to check IOs, reads, writes per table on mysql. So now ...
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240 views

configuration for max read throughput on ssd: pcie vs sata vs raid

I'm looking to configure a storage setup, using ssd's, that will deliver the fastest read throughput on large (2+ GB) files on a 24 core (12 physical core) system. The data is static for the most ...
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796 views

Why does a CP command on linux consume CPU?

I just run a copy command for two large directories with a small number of huge files and I see my cp process is consuming around half a core in top: 51116 root 20 0 110m 876 688 D 43.9 ...
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Resource monitor and how to spot if you have disk I/O problems?

I have an application server which runs pervasive SQL and app using it. Last weeks the users are complaining about poor performace of the app and I suspect disk I/O problems because CPU and RAM ...
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wait rate very high due to mysql server activity

Sometimes the server is very slow and needs a lot of time for serving the requests. iotop shows a disk read rate of 1-2 M/S on average for some minutes (which is not that much actually), after that ...
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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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Logging hurts MySQL performance - but, why?

I'm quite surprised that I can't see an answer to this anywhere on the site already, nor in the MySQL documentation (section 5.2 seems to have logging otherwise well covered!) If I enable binlogs, I ...
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Is a 'high' IO rate healthy?

I do a lot of work with my Linode that currently hosts a site, but every now and then (usually once every two months or so) - I'll get a warning about my IO rate being too high (Usually just higher ...
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Reducing IO caused by nginx

I have a lot of free RAM but my IO is always 100 %util or very close. What ways can I reduce IO by using more RAM? My iotop shows nginx worker processes with the highest io rate. This is a file server ...
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193 views

Delay before download starts when serving files using nginx

I am currently using nginx to serve downloads off my website. Users sometimes need to wait about 5 seconds before their download starts after clicking a download link. I'm not sure if I need to start ...
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897 views

Try to delete files used by IIS

I got a service coded in c# whoes deleted somes web site files hosted on iis, before an update. But sometime when i delete the files, they stay there. If I try to delete them manually, via explorer, ...
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DB Server Disk I/O utilization

I have a Linux server that I use to run the DB of my application (MySql), the server have 8GB Ram and 4 cores. there are no other applications running on the server besides the MySql. Most of the ...
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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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5.5GB written daily to 1.2GB root volume - 4 times previous levels

Problem: I recently revamped one of my servers, it was tested prior to use, and functions well, however, a few days ago, I noticed approximately 4 times the usual amount of writes to the root volume. ...
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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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663 views

How to track a single Xen VM's I/O utilization

What is a good way to monitor I/O individually for Xen Virtual Machines (not Dom0)?
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IO utilization percent of 4920.45% - iostat -x , What's wrong?

I have seen wrong percent use of a disk IO some times on servers that have been a long time without reboot. By any means this server has significant IO. Tonight it'll be rebooted and I'm sure ...
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How to analyze system calls when your disk is in read only and strace output is “Bus error”?

We have a HW problem with the disks, that made all the mount points to be read only. Output of dmesg: end_request: I/O error, dev sda, sector 15574609 sd 0:0:0:0: SCSI error: return code = 0x00040000 ...
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Utility for Monitoring IOPS on servers

We recently ran the Dell Performance Analysis Collection kit which monitors your servers via WMI for 24 hours. You send the file off to Dell and they return a report with graphs of IOPS and MB/S disk ...
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/etc/passwd continually accessed

I'm running a server on EC2 (Cent OS, 2.6.35.14, x86_64), and I recently went over my 1 million I/Os per month quota, which is absurd, as my disk utilization shouldn't be anywhere near that. (I'm not ...
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238 views

Good SAN sequential I/O throughput

We have an EMC San - CX4-240C filled with 15k (4Gb) Fibre Channel disks setup in RAID 5. Our applications that run on this SAN do primarily Sequential read and write of large text data files. I'm ...
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Possible disk IO problem. Help to be sure.

Since some time days ago, one of my servers started crashing. Currently it is crashing almost every day. Sometimes, over once a day. Only a restart can solve. The last time the problem happend, the ...
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How does Linux handle concurrent disk IO?

When a Linux server is serving many concurrent requests to read many different files, does it: Seek to File_1, read the entire file, then seek to File_2, read the entire file, then seek to File_3, ...
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575 views

Maximizing throughput of virtual file systems

I've been using a QEMU system to build software. The problem I've been having is that the system seems to suffer from extremely slow disk access. This is not necessarily a problem as it's not really a ...
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Disk IOs spikes at set times in CentOS

I recently installed Munin on my servers. Now 2 of my machines show big spikes in DiskIO at the same time, everyday at 4am. I run Centos 5.6 (64bit). I've checked my cron logs, and I have no personal ...
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Does DFS-R actually write 100%+change to a file on the receiving server(s)?

I am analyzing DFS-R on Windows 2003 R2 and have come across a horrendous thing. It appears that when you append a small amount of data to a large (existing) file, the write cost on the server for ...
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Monitorig ZFS io with Zabbix [closed]

I need to monitor per-zpool IO stats (number of reads, number of writes, size of reads, size of writes) with Zabbix. Is there a script for that? kstat provides only agregate data (all zpools summed ...
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iotop for Linux kernel 2.6.18

So it has to come to my attention that iotop isn't availalbe for 2.6.18 since it's less than 2.6.20 and requires Python 2.6+. I've done some research and came across this article: ...
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IO Speed virtual image vs Physical?

I am planning on building a Continuous Integration Server (the existing one is too slow). My plan is to run multiple OSes for our application testing on KVM. The structure will be a single physical ...
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kernel: scsi 0:0:0:0: rejecting I/O to dead device

Yesterday, OSSEC sent me an alerting email: Jul 29 21:25:16 SVR4149 kernel: end_request: I/O error, dev sda, sector 334634969 Jul 29 21:25:16 SVR4149 kernel: sd 0:0:0:0: SCSI error: return code = ...
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inonice not working properly in xen dom0

I have a Xen Dom0 (3.2) with a bunch of domUs (paravirt). DomU VBDs are on local LVM volumes. Now I want to get backups of the LVM volumes using snapshots. I use rsync ioniced to idle (ionice -c3). I ...
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IO and bus errors on Ubuntu Server

I've got an old computer running Ubuntu Server 10.04, which acts as router, file server and web server. A couple of weeks ago I inserted a PCIe video card, since the motherboard did not have any video ...
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In Windows Task Manager, in the Processes tab, what does I/O Other mean?

In Windows Server 2003, I'm seeing a process in Task Manager with a high value in the I/O Other column. I'm trying to determine if it's in some kind of error state, but I don't know what I/O Other ...
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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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How do you monitor the performance of a character device (e.g. tape drive)?

There are many ways to monitor block device performance: dstat and iostat, heck, even sar will give you data on block device I/O rates. Unfortunately, I don't know of any good spur-of-the-moment ...
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2answers
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Monitor Disk I/O Using DD

I've bee looking into the possibility that my server is experiencing a lot of iowait issues. I've found a lot online about running the dd command. I am unable to run this conv: [root@vps ~]# dd ...
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On Solaris, how can I tell what processes are doing disk i/o on a particular device?

On Solaris, iostat tells me that a device is 92% busy, but how do I find out what programs are making the requests?
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How to reduce mysql disk io?

mysql> explain SELECT * -> FROM (`items`) -> WHERE `states` = 'A' -> ORDER BY `updated_date` desc -> LIMIT 20520, 40; ...
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How to set i/o priority for nfs client processes?

The configuration is: A linux server and a nas box (netgear) acting as nfs server. It is easy for a single process on the linux server to use all i/o bandwidth by simply copying a file from the nfs ...
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What do the output values of dstat command mean when monitoring IO?

I am monitoring the IO and SWAP usage of a process in my backup server. I executed dstat -rs 5 and this was an example output: --io/total- ----swap--- read writ| used free 92.0 57.3 |3228k 514M ...
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Ramdisk vs Build-In IO Caching on Windows

I'm trying to understand the built-in IO cache on Windows. If an application writes to a file, and then reads/writes it multiple subsequent times, it seems that the IO cache should allow this to ...
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How can I get a list of Programs doing Disk IO?

I have a server (running CentOS 5) and I need to figure out which programs (MySQL, Apache, etc) are doing the most Disk I/O? Is there a command that will allow me to calculate an average over time?
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comparing disk performance of machines

I am in the process of moving applications running on old Linux machines onto VMs. As part of this, I need to justify the VMs have at least the capacity (i.e. CPU speed, RAM, disk, disk speed, network ...