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.

learn more… | top users | synonyms

2
votes
2answers
60 views

How do I check which files are written by an application?

On my system, sar reports an average write to disk about 5MB/s. Using dstat I found that it's not so permanently, but there are peaks to 30-50MB/s, and then are sleeps. Using iotop i found that most ...
4
votes
1answer
502 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). ...
1
vote
0answers
27 views

Inherit IO redirections from a script to another

When I redirect the output of a script within a script, I expect the redirection to be applied to the called script as well as the program called within it. A: ./B 2>> error.log B: ...
1
vote
0answers
11 views

Linux Mint keyboard and mouse take a long time to work after boot

I turn my computer on, select my linux harddrive, and then I end up at the Linux mint encryption password area. I have to wait about 1 minute just for my keyboard and mouse to actually light up and ...
16
votes
6answers
59k views

How can I read line by line from a variable in bash?

I have a variable which contains multiline output of a command. What's the most effecient way to read the output line by line from the variable? For example: jobs="$(jobs)" if [ "$jobs" ]; then ...
1
vote
0answers
10 views

If an I/O function cannot fail with EINTR, does that mean it never blocks? [migrated]

For example, consider fdopen. I have been wondering whether it's possible for this to block, if, say, the file descriptor argument refers to a pipe or socket. A Google search hasn't turned up anything ...
0
votes
0answers
10 views

How is a process state updated to blocked state (TASK_INTERRUPTABLE)? [migrated]

When a process is waiting for IO, how is the task state updated to TASK_INTERRUPTABLE (that is, blocked)? Imagine this case, a process issues an IO request to a block device. According to my ...
2
votes
1answer
43 views

Relationship between IO scheduler and cpu/process scheduler?

The concepts of IO scheduler and CPU scheduler confuse me. Below are my understanding: Linux uses CFS scheduler + nice values by default to schedule processes. Each process has an IO queue. There ...
2
votes
1answer
50 views

How to track down the source of I/O spikes?

I am using Linux as a desktop, and keep getting seemingly random I/O Spikes. The machine becomes unusably slow. At first I thought it was just that I don't have enough memory. But looking at the ...
1
vote
1answer
23 views

Set ionice for a multi-threaded application

I have a program that spawns multiple threads, all of which do fairly intensive IO, running on the background. I want to set the scheduling class to idle so that it doesn't clog up the system; ...
4
votes
4answers
1k views

Is setting a higher nice level for a process an effective way to reduce its impact on system load/CPU time?

I have an rsync cron job which is pushing the server load and triggering monitor alerts. If I set the job to be run with a high nice level, would that effectively reduce the impact it has on system ...
12
votes
2answers
9k 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 ...
35
votes
3answers
5k views

When is dd suitable for copying data? (or, when are read() and write() partial)

Short version: In what circumstances is dd safe to use for copying data, safe meaning that there is no risk of corruption due to a partial read or write? Long version — preamble: dd is often used to ...
3
votes
2answers
55 views

How does one determine when a process or machine is IO bound?

I have a node.js process which writes to many different sqlite databases. Sqlite can handle only one concurrent write per database, which is fine since there will be only one write per database at a ...
0
votes
0answers
30 views

stdin read notification

I want to detect when/if an application issues read(stdin, ...). Is it possible to use unbuffered I/O so that I could wait on write in external process? The problem: Some commands require user input ...
3
votes
2answers
44 views

How to determine whether the data is written to disk or cached?

I'm learning file operation calls under Linux. The read() and write() and many other functions use cache to increase performance, and I know fsync() can transfer data from cache to disk device. ...
0
votes
1answer
178 views

Does dm-multipath schedule I/O?

I have a multipath device I'm interested in: [root@xxx dm-7]# multipath -ll mpathf mpathf (3600601609f013300227e5b5b3790e411) dm-7 DGC,VRAID size=3.0T features='1 queue_if_no_path' hwhandler='1 alua' ...
0
votes
1answer
41 views

NAS: 100% system (kernel) cpu usage

I have a single core NAS My Live Duo. It runs Debian lenny release. I found via htop utility that it constantly use 100% of red cpu without any noticeable process to eat it. Than I checked via iostat ...
1
vote
1answer
56 views

Very slow file operation

I recently rebuild a machine with Centos 5.8 with a brand new disk. This machine is old and has been running 5.8 for a long period with no issues so the only thing which changed recently is the new ...
1
vote
1answer
38 views

Selecting IO scheduler on external drives

I'm running linux on the beaglebone black. My system is running directly from the sdcard. To change the IO scheduler I need to configure /sys/block/xxx/queue/scheduler where xxx is the mounted ...
2
votes
1answer
108 views

Set bash script output to the line that called bash script

I've looked for the greater part of two hours trying to see if I could find a way to redirect the output of a bash script to the line that called the bash script. The best example I can use to ...
2
votes
1answer
36 views

pipe speed benchmark with machine readable output

I'm looking for a tool similar to pv which is producing machine readable output. And i cant believe that nobody did it bevore... I looked at the manpages of pv, pipemeter, dd and cpipe but all these ...
8
votes
2answers
526 views

tar to pipe but keep -v verbose output separate from STDERR

A normal tar command tar cvf foo.tar ./foo >foo.out 2>foo.err has three output IO streams archive data to foo.tar list of filenames to STDOUT (redirected into foo.out) error messages to ...
2
votes
1answer
44 views

Running command on server, but have the server read/write local files [duplicate]

Is it possible to have a remote machine run a command, but redirect all reads and writes to a local machine. Example: I have a bunch of scripts in folder 'project'. When 'make simulate' is run in ...
2
votes
0answers
55 views

View syscalls/kernel activity for I/O from a running process

I'd like to be able to view syscalls or kernel activity for a process...I'm not actually sure of the terminology I need here! Specifically I'm looking for the difference between I/O going to local ...
2
votes
0answers
24 views

Linux sound lags while copying from USB key

Why did I experienced sound skipping while copying a big file from my USB key onto my computer's drive? I monitored the system during this I/O operation: music was playing from Internet on the ...
1
vote
2answers
668 views

Optimizing logical sector size for physical sector size 4096 HDD

With many new hard drive disks the physical sector size is 4096. Would it be possible to make the system use a logical sector size of the same size, rather than the default logical sector size of 512? ...
19
votes
3answers
4k views

Measure pipe throughput in the shell

There is a shell command that allows to measure how fast the data goes through it, so you can measure the speed of output of commands in a pipe. So instead of: $ somecommand | anothercommand you ...
2
votes
2answers
35 views

Current disk load

I'm using iostat to get the current disk load each second with iostat -dx 1 (specially, %util column). However, I'd like to put this in a bash script and control the interval with the watch command ...
0
votes
1answer
2k views

ERROR: init: ttyS0 (/dev/ttyS0) main process (1612) terminated with status 1

I'm getting the following errors every 10-30 seconds on a virtual Red Hat Enterprise Linux 6.5 2 Server on Amazons EC2. Sep 23 09:57:05 ServerName init: ttyS0 (/dev/ttyS0) main process (1612) ...
4
votes
3answers
106 views

Disallow File IO for a process except for FIFOs

How do you start a process that cannot do any file IO (opening / closing files, creating / deleting files, reading / writing files, etc.), except to read and write to pre-created FIFOs? (chroot will ...
2
votes
1answer
203 views

how to read any process' /proc/pid/io

I'm trying to monitor disk activity of each process. One way that I found how to do this is to read /proc/pid/io file and compare fields with previous read. That works fine except my monitoring ...
1
vote
1answer
42 views

How to collect disk read/write activity over a given period of time?

Sometimes, especially upon login, I have a lot of disk activity. I can use iotop to see what's doing that at a given moment, but I would like to have an integral table over a given time, say the first ...
4
votes
2answers
324 views

Disk busy is close to 100% and iowait is 0,0% on SunOS, how can it be possible?

During monitoring of SunOS5.10 machine I noticed strange behavior: Disk busy is close to 100% Disk waiting time is 0,0% Primary purpose of this machine is running application server on jvm. This ...
4
votes
1answer
583 views

Alternative to iotop for non-root user without sudo privileges

I'm looking for an alternative to iotop. Here's my situation: I want to find out if a program is accessing the hard drive a lot while running. iotop requires root/sudo privileges. My account is on ...
1
vote
1answer
165 views

why doesn't iozone generate output file?

I'm using iozone3 for tesing, on Xamin (an Debian-based OS). When I enter iozone command, for example iozone -Rab output.xls, the test runs successfully. But after running the test (after displaying ...
5
votes
1answer
128 views

Can you throttle the bandwidth to a tmpfs based ramdisk?

I created a ramdisk using tmpfs as follows: sudo mount -t tmpfs -o size=1024m tmpfs /myramdisk I was looking into cgroup blkio subsystem bandwidth limits "read_bps_device" and "write_bps_device" ...
2
votes
0answers
36 views

IO throughput lower when only a single process using the disk?

I am running a busy cacti server on centos and sometimes the rrdtool process is painfully slow when writing to disk, in HTOP the IO Column would display something between 100-300. I a polling cycle ...
2
votes
1answer
253 views

How to test Disk IO on VMs with iozone?

I want to test the disk IO performance like read, write, random read, random write and so on both in physical machine and VMs (with aufs file system). Also I want to test the throughput performance in ...
4
votes
1answer
338 views

How can I prevent disk I/O from taking over my CPU?

I run Debian Jessie on a quad-core i7 processor, which results in 8 cores being shown thanks to hyperthreading. On disk-heavy loads, all eight cores are maxed out with io-wait, as shown by htop. This ...
12
votes
3answers
15k views

Find out what processes are writing to hard drive

On my Lenovo T400 and Ubuntu, the light for hard drive writing keeps flashing. I was wondering if in Linux it is possible to find out what processes are doing I/O to the hard drive? Just like by top, ...
2
votes
0answers
82 views

How to calculate blkio shares in cgroups?

Currently I'm trying to setup a test scenario with the use of Debian Wheezy with its default kernel 3.2.60-1+deb7u3 and the cgroups blkio controller. The calculation of blkio.weight is not working for ...
3
votes
1answer
337 views

Removing redirection operator does not change output. Why?

I saw this usage of redirection somewhere, and thought it was a typo: grep root < /etc/passwd But after I run it, I saw that it gives the same output with grep root /etc/passwd: $ grep root ...
1
vote
1answer
501 views

External Hard disk Input/Output error

One of WD external harddrives is not working when I try to access some folder. I am able to access the rest of the folders on the disk. I am getting Input/Output error as show in the attached Image. ...
5
votes
2answers
1k views

Massive, unpredictable I/O performance drop in Linux

I'm using Debian testing without any problems for ~6 years (I'm just regularly updating it), but recently it started to show a random behaviour that can be summarized as "Low I/O performance which ...
2
votes
1answer
282 views

Dirty in /proc/meminfo for dd

I read from here that the below command gives me the amount of data that needs to be written to the disk. grep ^Dirty /proc/meminfo It particularly says Ever ask yourself "How much data would be ...
1
vote
2answers
171 views

mkfifo - Does disk I/O actually occur?

I have 2 applications: Producer (N instances) Consumer (1 instance) I currently write out intermediate results from the producers, and then the consumer reads these files from disk and produces a ...
0
votes
0answers
148 views

Journal commit I/O error for Seagate Expansion external USB hard drive

I am using Debian 7.6 (amd64) and for some reason when I am trying to read or write to my Seagate Expansion 1TB external USB drive, I am getting input/output errors ... Here is what the output of ...
1
vote
1answer
240 views

blktrace - differentiating between sequential to random io

I'm looking for a way to determine whether an app is doing sequential or random I/O. Is it possible to look at a blktrace capture and say if I/O is sequential or random? If yes, any examples of what ...
2
votes
1answer
1k views

jdb2 keeps Hard Disk busy all the time

My system became too slow last few days. The hard disk indicator is on all the time. To discover which process is keeping the disk busy i run this command: # while true; do date; ps auxf | awk ...