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

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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 ...
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MySQL, disk I/O and SSD drives

We have a LAMP box with 2x mirrored 1 TB WD Black Caviar disks running the whole OS and MySQL. 8 GB / RAM, 2x quad core CPUs. We're really taxed on disk I/O, and I've been thinking of ...
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How to measure IOwait per device?

I have a server, which exports home directories over NFS. They are on software RAID1 (/dev/sdb and /dev/sdc) and the OS is on /dev/sda. I noticed that my %iowait as reported by top and sar are ...
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Poor XFS performance — what's going on?

I recently formatted a 20TB array as XFS. For file transfers < 10G performance is fantastic. However once I exceed 10G disk I/O decays logarithmically. I have the journal on the same disk. When ...
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Dell PE2950 - slow IO rates for writing and reading locally

I'm having a serious issue with dell server PE2950. The server has really slow IO rates, so slow that I'm not able to use it anymore I tried few things to solve this: changing disks to new disks ...
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Benchmarking a hard disk drive for OLTP

I have a PostgreSQL database (OLTP, 10GB in size) server and I'm planning an array of hdds for it's storage. I have various disks I can use. I need to find the best ones for the job with the right ...
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NFS IO priority on ZFS/Solaris

I've got a Nexenta/ZFS NAS that I'm using as an NFS backing store for a small VMware vSphere farm. At the moment I have 9x1TB disks all mirrored (last disk is configured as a write log device). The ...
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Measuring Disk IO programmatically

I want to measure some numbers related to disk io in a given timespan, programmatically. This means I don't want to spawn a process like iostat to get my numbers, by prefer to read something from proc ...
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Scratch files in /tmp getting mysteriously deleted

I have certain files in a /tmp subdirectory that a script I wrote uses for scratch. The opens and closes these file perfectly fine for a few hours. Then, out of nowhere, the files are no longer found. ...
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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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Determine what's causing high disk IO

I'm having a problem with my VPS and disk IO. My server is running nginx + PHP-FPM + APC. The database is located on another dedicated VPS. I have several Wordpress MU sites living on the web server. ...
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High Disk I/O rate. How to investigate

One of my servers is getting very high Disk I/Os. The problem is that the disk I/Os are constantly increasing. The server just have simple LAMP configuration and there shouldnt be any disk operation ...
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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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High disk time on SQL Server

We have a dedicated SQL Server 2008 R2 Enterprise Edition. The setup is: D: (data files) - stored on local ssd disks (not the same disks as log files) (raid 10) E: (log files) - stored on local ssd ...
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High Load - Low IO - Low CPU usage

I have a system whose load is rather high. As you can see from the top output below, CPU usage and I/O is negligible: top - 17:31:59 up 4 days, 2:34, 2 users, load average: 1.00, 0.99, 1.00 ...
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VMWare Esxi Looking for Bottlenecks

I have a VMWare ESxi box, 22GB ram, Dual Quad Core Xeon, 2 Sas drives + Write caching raid controller etc. Anyways, have about 30 small XP VM's running on it and starting to get some very slow boot ...
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How to view formatted iotop log file in terminal with a cat

Hey there. So I have logged the history of Disk usage with a iotop > iohis.log How can I view the file so it is formatted nicely and I can actually find the issue. I thought I could use the cat but ...
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Estimate daily network IO between 2 servers

I have 2 servers : a database server (SQL Server 2008, called server A) and an application server (called server B) which send SQL queries to the first one. They are actually in the same LAN, but we ...
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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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IO-related lockups on a Xen PV guest running Ubuntu 10.04

I have a Xen PV guest, running Ubuntu 10.04. I do not run the underlying host. Kernel is the stock one provided by Ubuntu: Linux nephos 2.6.32-21-server #32-Ubuntu SMP Fri Apr 16 09:17:34 UTC 2010 ...
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Determining which process is causing heavy disk I/O?

I've seen this question: How to identify heavy write to disk? And I've used dstat and atop before...but they don't seem to pinpoint what process is causing disk I/O. For example, from dstat: dstat ...
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Will adding a SSD cache device to my ZFS storage improve performance?

The server has 4GB of RAM and my zpool is made up of 15.5k SAS drives arranged like this: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 raidz1-0 ...
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Can I set noatime for my XEN guest OS partition? Will it work?

I have a VPS in cloud environment based on XEN Virtualization platform. /etc/fstab looks like that: LABEL=PRGMRDISK1 / ext3 errors=remount-ro 0 0 As far as I know IO can pretty ...
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How do I tell which processes are writing heavily to disk in CentOS 5?

Our server started getting slow, so I ran iostat on it. iostat -dx 5 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 ...
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Does a read on a NFS file system slow performance?

If a NFS client reads a file, does any network traffic happen? or is it just writes (by any node) that result in network traffic? In particular, I'm interested in whether doing a file_exists() call ...
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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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Frequently accessed files and I/O usage

I'm curious, from a performance standpoint, is there an advantage in storing all files in one directory versus having each file in a separate directory? I'm not concerned about organization. Also, ...
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What types of IO does SQL trace display?

Are they physical or logical IOs? If they're logical, is there a way to break it out similar to STATISTICS IO for a production server?
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Linux Read-Ahead Downsides

Hope all is well. I have a question regarding read-ahead caching. Are there any downsides to raising the size of the read-ahead cache? On our farm, we're currently running at 256, and upon raising ...
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Windows Disk I/O Analysis

It appears that we are having a problem with the disk i/o speed on our Windows 2003 Enterprise Edition server (64-bit). As we were initializing a database that created two 1G tablespaces on 3 ...
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Debugging IO Limitation

I have a Fedora box with some severe IO limitations which I have no idea how to debug. The server has a Areca Technology Corp. ARC-1130 12-Port PCI-X to SATA RAID Controller with 12 7200 RPM 1.5 TB ...
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I/O Reads and Writes per process Unix/SunOS?

Can prstat or something similar tell me how many reads/writes a process is doing similar to how Task Manager on Windows can show I/O Reads, I/O Writes and many other I/O columns per process? I'm ...
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Possible disk IO issue

I've been trying to really figure out what my IOPS are on my DB server array and see if it's just too much. The array is four 72.6gb 15k rpm drives in RAID 5. To calculate IOPS for RAID 5 the ...
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lsass.exe high I/O with SQL Server 2005 sp3

Hi I have a SQL Server 2005 Enterprise Edition on a Windows Server 2003 Enterprise sp2. Lately, I get very high I/O(Reda, Write, Other in Task Manager) from process lsass.exe. When I run sysinternals' ...
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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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What program in Linux can measure I/O over time?

I'm trying to measure the total amount of disk writing and reading that is done to a particular volume by a particular process over a specified duration. I've found iotop, which can output IO every ...
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CPU or network I/O bound?

I'm trying to find out whether my server is network IO bound or CPU bound. I did look at the output of some of the typical tools to check the current status of the system (output of iostat, sar and ...
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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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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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How to track cause of blocking IO problems

I move between multiple subnets and networks on a regular basis. I'm often faced with Explorer and other programs that stall in what appears to be an IO request. I'm trying to find a consistent way ...
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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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Exchange 2003 I/O Troubles

We have some internal processes that send email to our Exchange 2003 system (on Win2K3 R2 32bit). Recently they have been intermittently failing with various errors -- boiled down they report ...
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Find the bottleneck: disk I/O on Windows XP

One of our development boxes has developed a problem wherein performance will occasionally drop through the floor. When this happens, you can hear the hard drive thrashing, but I don't know what's ...
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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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How to identify I/O bottlenecks on a Linux server?

How do you determine that the performance of your Linux server is I/O bound and, perhaps more importantly, what process or processes are casuing the problem?