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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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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What are front merges in I/O scheduling and how can I tune this parameter? [closed]

My Linux uses the Deadline algorithm for I/O scheduling. One of the parameters is the front_merges parameter under /sys/block/sda/queue/iosched/front_merges. By default it is set to 1, which means ...
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25 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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1answer
17 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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44 views

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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37 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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8 views

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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23 views

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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31 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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29 views

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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21 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
94 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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1answer
59 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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0answers
59 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 ...
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1answer
70 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 ...
4
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1answer
25 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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1answer
28 views

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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33 views

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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69 views

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
79 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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1answer
76 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 ...
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52 views

How to get the Serial Number of a disk by corresponding file in linux?

I know that for a disk in linux, we can use commands such as hdparm or smartctl to get its basic information. But for the implementation of these commands, I think all of them are implemented by ...
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30 views

Samba system calls for reading/writing files from/to NAS issued from Windows desktop client

Windows desktop machine is connected via 1GB Ehternet cable to personal NAS (under development) with Ubuntu on it. While reading and writing files (> 1GB size) from/to NAS strace was conducted to ...
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42 views

Linux huge IOPS difference - same disks

I've been investigating for some time regarding some IOPS issues I've been experiencing.. And my mind is getting crazy! I have two servers (one bought 2 weeks ago, another 1.5 years ago) that I ...
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23 views

Restoring in-memory/swapped page state on resume from hibernation

I'm a big fan of Linux's hibernation support, which works extremely well on all the (admittedly slightly older) hardware I've tried it on. I highly prefer it to full shutdown and power up. There's ...
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56 views

how does o_sync trigger pdflush?

When I write using o_sync, the write call returns once the data has been written to the disk. But how does o_sync force Linux to write the data to disk? Normally you would have to wait a maximum of ...
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24 views

SSD as write target during reads

I have a real-time application which always writes data to a RAID 10 HDD configuration in a sequential manner at around ~50 MB/s. It uses mmap and writing should never be blocked due to waiting I/O. ...
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251 views

Monitor a program's I/O

I have a program which spawns several child processes. I want to know which files this program and its children are creating, deleting, and modifying. inotifywait can tell me which files are being ...
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59 views

iowait monitoring in top on OSX/iMac

I'm trying to monitor the performance of a process on OSX 10 (iMac), specifically whether I/O is currently a bottleneck or not. I don't use the machine, hence I need something simple that the user can ...
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24 views

IO benchmark tools block size impact?

Many IO benchmark tools (fio, dd, etc...) provide way to set block size. Lets say that I change 4K to 64k and test read/write on mounted SATA disk. I will get higher data throughput in sequential ...
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1answer
83 views

Tuning Linux I/O Scheduler

I need a little help with properly tuning the Linux I/O Scheduler for spinning drives. I have a process that writes data to a huge (4-16TB) memory mapped file and is using SHED_FIFO. The kernel then ...
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558 views

What's the difference between ioremap and file operation mmap?

I'm currently working on a PCI device driver for Ubuntu. I have some example code about PCI driver, but I have difficult on understanding the ioremap and file_operation.mmap. The description of file ...
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mmap and slow DMA transfers

I have a process that reads data from a hardware device using DMA transfers at a speed of ~4 * 50MB/s and at the same time the data is processed, compressed and written to a 4TB memory mapped file. ...
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1answer
69 views

iotop and ionice -p show a different class/priority for the same process

After running ionice -c2 -n7 <PID> on an I/O-intensive process (VirtualBox VM) and checking the result with ionice -p <PID> it shows best-effort: prio 7 which is expected. But when ...
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1answer
54 views

How to prevent dd from freezing my system?

I want to fill the free space on my hard drive with a command like that : # dd if=/dev/zero of=z but it causes GNOME to freeze regularly for a few seconds. Even the mouse cursor is affected. How ...
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203 views

Accessing Memory Mapped I/O is slow

I have a Terasic-SoCKIT(fpga & arm cortex a9) and I have Linux running on the HPS. I'm trying to access the memory mapped I/O, wrote a simple character driver with functions "request_mem_region" ...
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1answer
322 views

How to find what is hammering my I/O?

On a Ubuntu Linux machine that is used as a webserver, I see that I'm really hammering the I/O: - dysphoria():~$ iostat -d 3 3 Linux 3.13.0-45-generic (dysphoria) 2015-10-20 _x86_64_ ...
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Disk benchmark IO depth clear out

When I'm manipulating over some benchmark tool I/O depth, what exactly am I changing? Let's say I have SATA disk on /dev/sda. If I run hdparm: root@linaro-gnome:~# hdparm -I /dev/sda | grep Queue ...
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1answer
84 views

How to force ssh-add to ask passphrase when loading RSA key from FIFO?

I've created the following RSA key (with passphrase): ssh-keygen -t rsa -f rsa_foo Now when adding the key in normal way, ssh-add asks for the passphrase fine: $ ssh-add rsa_foo Enter passphrase ...
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1answer
48 views

How would I monitor the running i/o statistics of an application?

In windows I find it incredibly useful to monitor total I/O read bytes to give myself an idea of how long a command line process is taking/will take to execute a task. For example, for capinfos: ...
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2answers
78 views

Bash passing input

I am using an open source tool to merge files with genomic ranges (Feature to similar to R language function 'merge'). The software can take only two input files at a time. Suppose if I have to merge ...
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1answer
64 views

where or how to see if data is still being transferred over usb to mass storage

The data transfer to my mp3 player is very slow via USB connection. I have a mp3-player from Samsung (YP-M1JCB/EDC) which I have connected to my Fedora linux (the pc connection in the mp3 player is ...
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1answer
81 views

How to know which programs support streaming I/O

As I understand it, programs that support streaming I/O can work with files more than the size of the memory. Is this correct? Is there a way to know which programs support streaming I/O?
2
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1answer
61 views

Why is IO so high when almost out of memory

On my work laptop with an SSD and no swap, I sometimes run out of memory when running RAM-expensive applications (virtual machine, etc). When that happens, the system becomes slow (expected) but what ...
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1answer
2k views

How to get total Read and write IOPS in linux

How do i get Read and write IOPS separately in Linux? using command line or in a programmatic way. i am installed sysstat package. Please tel me how do i calculate separately using sysstat package ...
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11 views

Can suspending lead to data loss on an external HDD?

Let's assume we have an external HDD using an ext4 filesystem, powered via USB. Some write is ordered on the external drive, not synced yet. Then the user wants to suspend the system. Provided no ...
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5k views

What's the philosophy behind delaying writing data to disk?

In Linux, a finished execution of a command such as cp or dd doesn't mean that the data has been written to the device. One has to, for example, call sync, or invoke the "Safely Remove" or "Eject" ...
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195 views

Disk I/O latency using /proc/vmstat file

How do I calculate disk read and write latency in Linux? Is it possible to do the calculation using /proc file system? I am using iostat and vmstat command. But I do not understand how the ...
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1answer
196 views

Linux Performance Measurements using /proc/vmstat

Am new to Linux, Please any one help. I want to calculate Input output performance using /proc/vmstat file? when i run command cat /proc/vmstat | grep pgpg The answer is pgpgin 726854 pgpgout ...
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924 views

CentOS 7 Live - Read-only file system error

I have loaded a CentOS 7 Gnome Live USB. I wanted to do some operations on it without touching the installed system on the computer, because I only want to try some things. I installed openssh-server ...