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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Force dirty pages limit in kernel sources

First of all, I'm not sure if that's a solution to my problem. My problem is that during I/O embedded linux is allocating too much memory in cache causing OOM if I run anything else. I/O operations ...
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40 views

How can I differentiate disk I/O occured explicitly by a user and OS prefetching?

I am monitoring disk I/O usages of an application program (running on CentOS 7) It uses lots of sequential disk I/Os where I expect that OS prefetching is something! dstat shows how many disk I/Os ...
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427 views

How to tell if a character special file would block if read from

I would like to be able to tell if a character special file would block if a character were read from it without actually reading a character from it. Can this be done?
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63 views

How to tell whether a process is network I/O intensive or not in user mode in Linux?

I am currently writing a program in Linux which needs to tell whether a specific process is network I/O intensive or not at runtime. I have tried some tools such as iotop and iftop, but none of them ...
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1answer
18 views

Very low disk performance on Samba

I'm using Samba on Debian 8.4 (Jessie) to share files with a small number of Windows & Mac users (~20 total, ~5 at a time at most) and I'm seeing abysmal performance on read and write: tested by ...
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Samba performance tuning

Hi I'm using Samba to share a folder from linux to a Windows client(Windows Server 2012 R2). The disk backing the linux share is pretty fast (NAS of 500+ MB/s). However, when I benchmark the IO ...
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70 views

Slow USB 3 write speed

Writing to my USB 3 thumb drive (SanDisk Extreme SDCZ80-064G-FFP) is very slow on Linux: 1 GB takes longer than 200s. Using Windows (dual-boot on the same computer), the same 1 GB file can be copied ...
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iozone read test slower than fio

I'm currently using both iozone and fio to test my disk performance. However, iozone show much much poor speed than what is shown from fio. (about 1/3) Now the question for me is which number should ...
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44 views

Persistent process substitutions? [duplicate]

Is there a way to take a process substitution like <(grep foo some/file), and save it to a "file-like entity" on disk (reminiscent of a fifo), so that, every time this thing was opened for reading ...
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1answer
33 views

How does iotop calculate the relative I/O activity?

I am running some heavy I/O processes on my workstation and recently installed iotop to monitor them. Here's a recent screenshot: I'm a bit confused about the readings in the IO> column. It ...
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Arch Linux: blk_update_request: I/O error, dev sr0, sector 1452024: unrelated to user input

I just left my Arch Linux installation running in a virtual machine. When I came back to it, I found the following error: [14554.169929] blk_update_request: I/O error, dev sr0, sector 1452024 [14554....
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31 views

Sometimes syncing gets stuck with dd

Sometimes when I use dd then sync or use dd with conv=fsync, the syncing process gets stuck, but sometimes not, with exactly the same input and output targets and configuration. dd if=2016-03-18-...
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1answer
64 views

Monitor temperature/IO of NVMe drive

Is there a way to monitor temperature or reads/writes of and NVMe drive (in this case Intel 750). hdparm, udisksctl, smartctl, and hddtemp all seem to lack this capability, google searches have been ...
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26 views

Determine affected file given logical block number [duplicate]

Given the logical block number from these log lines in /var/log/messages, is there a way to determine what file was affected? ...Buffer I/O error on device sdd1, logical block 203953715 ...lost page ...
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1answer
24 views

How to clear data from all files present in a directory?

I have a folder which has some text files and other folders in it which in turn have more text files in them. I need a command which will recursively loop over the folder and clear all the contents ...
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53 views

Why does hdparm and dd show two completely different results?

I have an external hard drive (/dev/sdc1) mounted at /mount1 When running hdparm -tT /dev/sdc1 I get: /dev/sdc1: Timing cached reads: 2246 MB in 2.00 seconds = 1123.75 MB/sec Timing buffered ...
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74 views

Create a file of fixed size with specific contents

I want to create a file of fixed size (1G, 10G, 100G etc) with a single random word of length within the specified limit on every line. I basically want this to run a benchmark which will sort the ...
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2answers
64 views

Defer *all* disk writes, keep them in memory

How to temporarily stop synchronizing of dirty data with disk, instead just keeping it in memory. Clarification: I want to sync it later.
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113 views

How to redirect STDIN of background process?

In my Ubuntu, i run java application in background. I use bash script to run it and now it looks like: nohup java -jar app.jar & exit 0 The problem that i want to be able to write an input ...
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31 views

How do I give an input to an infinitely running program? [closed]

I have a python program that runs infinitely, takes an input and throws an output. I want to write a bash program that gives an input while the python script is running. So, how do I give an input to ...
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22 views

Diagnose input/output errors on a Truecrypt container

I have been trying to get a local repository located on a usb drive working on an air-gapped machine. The repository was created with apt-mirror on the same kind of system (ubuntu i386). Currently I ...
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2answers
89 views

What does the symbol '-' mean in Linux? [duplicate]

I see this symbol all the time and my book has yet to clarify what it means. None of the man pages or web searches clarify this either. At first I believed it to be a I/O symbol, but that never works ...
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113 views

Input/output error, cannot install anything

I have done something strange to my debian server and now I cannot install anything. It says, that locale is broken. I tried to fix it by reconfiguring dpkg, cleaning apt-get and and many other ...
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89 views

command to list logical volume I/O statistics on AIX

I am looking for a command which displays the I/O statistics of logical volumes (like reads/sec , writes/sec, io utilization %, read kb per second, written kb per second) . I tried iostat, but its ...
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117 views

The interrupt timeline for a single process doing output

I'm studying the book 'Operating System Concepts' 9th edition. In the first chapter, part 1.2.1 computer system operation, I can't understand the figure 1.3: Can any one make a quick interpretation ...
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27 views

How do I hook an application and find out what files it writes while running? [duplicate]

I'm not sure how to exactly word this question, because my searching hasn't yielded anything that describes my situation what I'm looking for. Say my friend writes an application and sends it to me ...
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1answer
56 views

Why is uninterruptible sleep indicated by 'D'?

From "man ps": R = Running or Runnable S = interruptable Sleep T = sTopped Z = Zombie D = uninterruptible sleep (usually IO) Where does this D come from?
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1answer
27 views

Crash with input/out error and swap unmounting [duplicate]

I am looking for hints on this problem. I've searched around, but can't find something exactly similar. I am running Debian 8 stable, updated, very minimal install (i3wm, small number of apps running)...
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93 views

Desktop completely freezing on I/O operations

In my old system, I was already having desktop freezes on some heavy I/O operations like apt-get dist-upgrade and copying 4 GB video files. But now, it has become a lot worse: any apt-get install is ...
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1answer
39 views

understanding lsof during long operation on big file

Background I'm running Musicbrainz Picard to update a ~11M ogg file on a 500GB NTFS disk (Transcend StoreJet) connected via USB and mounted using autofs. The connection is through docking station. ...
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3answers
419 views

How do I run a command in a different tty?

Suppose there are two terminals, pts/0 and pts/1. In pts/0, I have fired a command: ls>/dev/pts/1 Then, we only get the output of the ls command in pts/1, but I want to run a command as well as ...
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79 views

copy and symlink mysql to another disk partition

I'm using ubuntu 12.04 and have two disk partition named: /dev/sda and /dev/sdb. my home partition and other programs are in /dev/sda. therefor any work like database benchmark on my mysql databases ...
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65 views

Which components of Linux IO subsystem are device-independent and device-dependent?

From Tanenbaum's Modern OS, every operating system has an I/O subsystem for managing its I/O devices. Some of the I/O software is device independent, that is, applies to many or ...
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Linux: Why do init and systemd use so much I/O?

This is probably unanswerable. But maybe someone else will have this problem and find this question, append to it, or proffer an answer. I discovered the pidstat command with its -d option, today. ...
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40 views

Input redirection using command and options

I am trying to write a script that takes in 2 parameters - program name and optional flags. I am trying to execute the program command on an input_file and store the output in the output_file. $...
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how qemu interacts with guest os io requests?

the Linux io stack (eg the path of an io request) is something like this: now when such a guest OS is a Linux distro in qemu, the path is the same except in this case there is no disk and scheme is ...
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Dive into qemu source code to trace io requests

I searched a lot about qemu and read its documentation but could not find any explaining its I/O stack. Specifically, I want to know about how an I/O request is created and what path it travels to ...
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45 views

dd process real vs. sys time

I have two quad core workstations. One is based on Intel Atom x86_64 architecture (WS1). Another one is based on armv7l architecture (WS2). Both are running 3.10 kernel version. Identical busybox dd ...
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Why my disk is at full speed even though very little is written or read?

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 429.60 9.00 170.20 2.00 2479.20 71.20 29.62 10.80 67.28 ...
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59 views

Storage device trouble: IO errors but no bad sectors?

I have a lightly used spinning metal drive (internal) with some VMs on it. I'm running into IO errors while running a VM and upon closer examination I have found a virtual disk file that is reporting ...
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1answer
103 views

Does hpdarm -Y suffice to stop IO on my hard drive?

I'm using Ubuntu 14.04 with two hard drives in my laptop. The first contains my root partition and my home partition. The second one is used for backups only. I know that hard drives break down after ...
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143 views

find which process is sending the current io request in linux kernel

I've been diving into the Linux kernel. and would like to trace an io request and find out exactly which process sent the current io request? There is a structure named current which the kernel ...
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1answer
433 views

hdparm: SECURITY_SET_PASS: Input/output error

I'm trying to use hdparm to secure erase an SSD as suggested here. Following the directions in that guide has worked okay so far, but I can't seem to resolve this error: ~ $ sudo hdparm --user-...
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1answer
215 views

Serial port - no output Penmount DMC9000

I'm trying to read some data from the some serial ports (I need them to deal with a touch screen controller). What I'm basically doing is cat /dev/ttyS0 to see what does the serial give as output ...
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1answer
45 views

Cannot reformat Micro SD Card

I need to reformat my micro SD card, however I am having some issues with it. When I go the card on my computer, it displays the following message: The folder contents could not be displayed ...
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which section of kernel, manages io requests?

I know that the Block IO layer in Linux io stack manages and schedules io requests. but i do not know where is this code? indeed, i wanna see the section of code in kernel which corresponds to this ...
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LVM Logical Volume (linear) best performance

As a system administrator, one thing I do very often is increase LV's size. In most cases I have to extend first the VG, adding a new disk (we are talking about virtual machines). I have got a lot of ...
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In which thread does block driver issue commands to block device?

I'm currently reading "Understanding The Linux Kernel" book, as I've understood block I/O request order is like this; user space call => vfs call => I/O scheduler call => block device driver call. ...
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1answer
313 views

iotop showing 1.5 MB/s of disk write, but all programs have 0.00 B/s

I don't understand iotop output: it shows ~1.5 MB/s of disk write (top right), but all programs have 0.00 B/s. Why? The video was taken as I was deleting the content of a folder with a few millions ...
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219 views

Why is OS constantly writing to disk (ext4) on a Ubuntu 14.04 machine? Is it normal?

I'm quite sure it didn't happen before I started using LUKS and LVM on my disk (2 or 3 weeks ago), but now root user is constantly (every 2-3 seconds) writing (not reading, just writing) on disk and I ...