I/O is an acronym for Input/Output, which refers to the mechanism or process for the transfer of information between one system or component and another.

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Determining Specific File Responsible for High I/O

This is a simple problem but the first time I've ever had to actually fix it: finding which specific files/inodes are the targets of the most I/O. I'd like to be able to get a general system overview, ...
1
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1answer
428 views

-bash: /usr/sbin/useradd: Input/output error — What does this mean?

Today, on my Centos server I tried to add a user but got the following error: -bash: /usr/sbin/useradd: Input/output error How do I fix it?
3
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2answers
123 views

How to make directory modication date change when files from that dir change?

For example, if a file has been changed in that directory, then directory modification date should be updated. Basically any changes that happen in that directory should trigger a "touch" on the ...
2
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0answers
580 views

find ount what [flush-8:0] is writing

Using iotop, I found out that [flush-8:0] is doing a lot of hard disk activity, which explains the annoying slowdowns. However, I can't figure out what's the actual cause behind this flushing. No ...
4
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2answers
240 views

Why do systems become slow when doing massive writes to disk?

I want to know why systems become slow when writing mass data to disk. I think that for system to become slow, there should be some issue with CPU. But write is only I/O bound. Do hardware ...
2
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0answers
102 views

Shorter timeout on I/O errors MacOS X

How do you set a shorter timeout value for read/write I/O errors on MacOSX? We tend to get a few semicrashed disks and want to rsync the contents to a secure location, but when the file subsystem ...
2
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1answer
151 views

CONFIG_GPIO_SYSFS makes /sys/class/leds disappear

I have an embedded Linux board I'm working on, with a button and a couple LEDs. By default, I can control the LEDs via /sys/class/leds/redled/brightness However, I have no way to monitor the ...
0
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1answer
118 views

Unable to delete a directory even as root

I am unable to delete a directory even as root. The command rm -rf kdyiyv.pif returns nothing. Then I tried the command, touch kdyiyv.pif for which there was an error: touch: setting times of ...
4
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4answers
822 views

Special File that causes I/O error

I want to automatically test if a piece of software reacts as expected if an essential SQLite DB file fails to be read (causing an I/O error). Exactly that happened some days ago at a client. We ...
20
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3answers
1k views

Can the “du” program be made less aggressive?

We have a regular job that does du summaries of a number of subdirectories, picking out worst offenders, and use the output to find if there are things that are rapidly rising to spot potential ...
1
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1answer
116 views

Determine how much a process is using each disk?

How do I tell how much load a particular process is contributing to each of several available volumes/mounts? It seems that dstat only shows aggregate stats across all processes per disk, and iotop ...
4
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2answers
501 views

iotop but for particular disk?

Is there a tool like iotop but for monitoring IO on specific volumes? (Or perhaps I missed a way to filter iotop?) If not is there any way to get at this information via (say)/proc? (dstat etc. ...
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1answer
3k views

I/O errors on hard disk on Linux boot

Here is a screenshot of booting Arch. I guess the reason is that I force poweroff my Arch linux many times. (I already force poweroff my Arch because my firefox flash plugin use too much memory to ...
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0answers
1k views

How to set up ZFS with ZIL and L2ARC SSD?

I have been considering bcache and flashcache. However my friend suggested me something called ZFS. In fact it says that formating disk with ZFS can actually do the exact same thing without kernel ...
3
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2answers
587 views

Storing thousands of files in one directory

I have a web-site that I'm checking for performance issues and bugs, and i came across a caching code that caches thousands of files into one single directory. I understand that this is not good and ...
6
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3answers
252 views

Why is I/O uninterruptible?

What is the rationale behind making I/O uninterruptible? What would be the negative consequences if a process handling I/O were allowed to handle a signal?
5
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2answers
329 views

How to improve IO when there is a lot of random read and write?

My scripts uses tons of read and writes. Most of them are small and random. I want Linux to wait 10 seconds before writing any data to the disk. How would this be achieved? I think Linux can already ...
0
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1answer
339 views

Does linux have something like supercache?

I installed http://www.superspeed.com/desktop/supercache.php for windows and the result is awesome. Every program I run is faster. Basically it uses the memory to cache data. Simple idea. I also use ...
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1answer
95 views

Strange IOStat xk. Moving a mere 40GB data is too slow. Can anyone explain?

iostat -xk 5 avg-cpu: %user %nice %system %iowait %steal %idle 0.99 0.00 1.10 11.01 0.00 86.89 Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s ...
0
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2answers
271 views

is writing to slow storage in nohup mode blocking the process?

If I have a process writing to nohup and the storage where it writes to is slow, does it block the process which is running in nohup? For example: process A is running in nohup, it needs to write 10 ...
2
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1answer
125 views

IOStat report large ocassional writes but find reports no big file

root@host [/home4]# find . -type f -size +2000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }' ...
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2answers
770 views

How to know recently updated files

If I run iostat -x 1 I saw ocassionally large 5MB to 10MB writes. What files are being written? I want to check the recently created files with size over 5MB for example. How would I do so?
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1answer
227 views

iostat report huge writes to drives that's not even mounted

root@host [~]# fsck /home2 fsck from util-linux-ng 2.17.2 e2fsck 1.41.12 (17-May-2010) /dev/sdb1: clean, 6018617/91578368 files, 54524459/366284000 blocks root@host [~]# fsck /home4 fsck from ...
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1answer
2k views

Which drive had a “journal commit I/O error”?

I received a message: kernel:[123456.789012] journal commit I/O error Which disk drive had the journal error?
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2answers
155 views

Determine which process is taking most of disk bandwidth?

When the HDD indicator is blinking (for a long period), how could I know which process is taking most disk bandwidth?
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1answer
161 views

Does symlinking from Drive A to Drive B affect I/O on Drive A?

I was wondering if IO through a symbolic link affects IO on the host drive even if it points to a seperate drive? My setup is, /dev/sdb2 1.8T 443G 1.3T 26% /home1 /dev/sda3 1.8T 1.7T ...
16
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1answer
2k views

Meaning of colours in htop

Given the option: [ ] Detailed CPU time (System/IO-Wait/Hard-IRQ/Soft-IRQ/Steal/Guest) In htop (Version 1.0.1) what are the meanings of the colours? In the following image, I'm seeing rather a lot ...
2
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1answer
1k views

I/O error but no bad block is reported in syslog

I got errors like this in my syslog, but there's no bad block or sector defined in kernel report, I can't just replace the HDD right now and I prefer to reallocate the bad blocks for now, so I need ...
12
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2answers
3k views

Can I watch the progress of a `sync` operation?

I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that ...
9
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2answers
5k views

How to Throttle per process I/O to a max limit?

I'm looking for a way to limit a processes disk io to a set speed limit. Ideally the program would work similar to this: $ limitio --pid 32423 --write-limit 1M Limiting process 32423 to 1 megabyte ...
3
votes
1answer
144 views

What is the difference between > and >> (especially as it relates to use with the cat program)?

Suppose that I have a file called temp.txt. Using the cat program, I would like to add the contents of this file to the end of myfile.txt -- creating myfile.txt if it does not exist and appending to ...
8
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2answers
851 views

What keeps one side of an rsync so busy?

I've got a Debian machine on my LAN serving as a backup server for the others. It has four HDDs combined into a software RAID 5 md device, on that an LVM, and on that btrfs. Backups are made using ...
3
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2answers
389 views

Running jobs in parallel on Ubuntu - I/O contention differences between Perl and Java

Apologies if this is off topic - it concerns the relative efficiencies of running I/O-heavy Perl/Java scripts in parallel on a Ubuntu system. I have written two simple versions of a file copy script ...
5
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3answers
407 views

File size of 60.0 PB is wrong. Can deleting it cause data loss?

While backing up some data (a 200 GB home directory) with rsync, I got an I/0 error for a particular file, after which rsync continued on "normally" with its backup. The problem source file showed as ...
2
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3answers
634 views

How can I read lines at a fixed speed?

I need to read a large log file and send it over a local network using (netbsd) netcat between two VMs on the same host workstation. I know that netcat has an interval, but as far as I can tell, the ...
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2answers
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Portability of “> /dev/stdout”

Occasionally I need to specify a "path-equivalent" of one of the standard IO streams (stdin, stdout, stderr). Since 99% of the time I work with Linux, I just prepend /dev/ to get /dev/stdin, etc., ...
4
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4answers
840 views

script for logging all the stats for a particular process

I want to monitor CPU usage, disk read/write usage for a particular process, say ./myprocess. To monitor CPU top command seems to be a nice option and for read and write iotop seems to be a handy ...
3
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2answers
864 views

I/O statistics per user

I have access to an academic supercomputer where there is an NFS filesystem where our lab keeps our data. When I run iostats -nh I believe I am getting statistics for all users accessing all storage ...
2
votes
1answer
256 views

How do I record disk performance on slow hardware and then replay it to faster hardware and benchmark it?

I am currently performing various development tasks that are slow on my current system because of IO performance. Is there a way to record disk operations while performing IO consuming tasks, ...
21
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3answers
723 views

How can I limit the output speed of stdout?

I'm running CentOS 5.7 and I have a backup utility that has the option of dumping its backup file to stdout. The backup file is rather large (multiple gigabytes). The target is an SSHFS filesystem. To ...
4
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2answers
3k views

Write inside a socket open by another process in Linux

Is it possible on Linux for a process to write inside a socket open by another one? Let's say I open a connection to google.com using netcat: myuser@linux:~$ nc google.com 80 Now I can lookup for ...
2
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2answers
1k views

vmstat IO stats: why the high bo during a download?

On my RHEL 4 machine, I was downloading a huge file (2.5GB)..I was checking the output of vmstat and was especially curious about seeing the disk IO using bi and bo. I know iostat is a better tool ...
6
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2answers
376 views

Mysterious write IO

I am just reviewing the disk IO of a XEN VM server. I stumbled across a DomU that has constant write traffic. To narrow that traffic further down I logged in to the DomU (CentOS 5, 64 Bit) and ...
5
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1answer
824 views

SysBench highlighting abysmal disk write performance on white box vs Tier1 server

Have been testing white box system with SuperMicro X8DTL motherboard with various SATA hard disks such as 7,200RPM Seagate Constellation ES and 10,000 RPM Western Digital VelociRaptor. Have tested ...
4
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2answers
2k views

100.0%sy with poor disk performance

I have RHEL 5.4 kernel 2.6.18-164.el5 and I am experiencing very bad disk performance that happens randomly during working with Oracle. Nothing appears in the logs. When it happens, I see one CPU ...
3
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1answer
105 views

Copying a file that is written at the same time

This related question can't solve my exact problem, so I'm writing a similar question. My scenario is the following: a program (run by wine) writes to a file sized about 10-500 KB. About 1 KB ...
2
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1answer
122 views

In terminal, I can search to end of log faster than the data gets there

[The Question] Is there some way to have the pipe/tee/write combo write lines immediately? ... if it can be done, what is the trade-off? [The Backdrop] My script sends a keypress to the terminal, ...
3
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2answers
96 views

dealing with un-executable commands inside a shell-script

I am given an assignment like this: Write a Bash script that takes a *.tex file as command-line argument and checks if the file executes correctly without any errors. If it executes without any error ...
4
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1answer
976 views

Why do backgrounded processes sometimes stop spontaneously?

Sometimes, some time after I've backgrounded a process with bg in bash, when I press Enter in the same shell to redisplay the prompt (just to check that I'm still in bash when some output from the ...
2
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0answers
448 views

GNU/Linux, IO performance problems

I have some problems with my system performance. As I was adviced here, I used sar: $sar -u 5 and found out that the problems are caused by a low HDD performance, as I supposed (high %iowait). ...