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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30 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 ...
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1answer
31 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
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2answers
78 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 ...
3
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1answer
55 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
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1answer
50 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
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1answer
75 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
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0answers
28 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
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1answer
105 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 ...
3
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1answer
95 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 ...
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3answers
13k 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
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0answers
40 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
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1answer
326 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 ...
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1answer
179 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. ...
4
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2answers
745 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 ...
0
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1answer
702 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) ...
2
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1answer
147 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 ...
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2answers
65 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 ...
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0answers
109 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 ...
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1answer
88 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
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1answer
881 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 ...
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4answers
2k views

Can I just disable updatedb?

Is updatedb necessary at all? I never use locate and my servers tend to have dozens of millions of files which usually makes updatedb to run for a long time and consume I/O needed by MySQL and/or ...
2
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1answer
108 views

Spawn multiple dirty page flusher threads per device

In earlier 2.6.X kernels, pdflush was used and it would spawn more pdflush threads if all current pdflush threads were busy for a second (read from The Linux Page Cache and pdflush). Since the ...
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1answer
107 views

wget internal buffer size

I'm constantly using wget to download many files over 1GB each. I'm getting concerned about how this may be straining my HDD. Can wget's internal buffer size be modified so that it writes to my HDD ...
7
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2answers
275 views

Reduce bad block retry / wait times in Ubuntu

How can I reduce the IO wait time and retry times so that the OS doesn't continually try to write to a failing drive? I have an system that I use to make copies of demo content that gets loaned out ...
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0answers
153 views

/dev/sda not appearing after secure erase

I decided to wipe my SSD with a secure erase before installing Arch Linux, since the Arch wiki said that it would improve performance. I followed the instructions listed on the wiki, but now when I ...
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1answer
48 views

prevent filesystem access while passing information to and from programs [closed]

I have written a main script that calls a system program tens of thousands of times. The main script creates and provides this program with an input file on each call. Upon completion, the program ...
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1answer
49 views

How to decrease the time the processes would wait (blocked) for disk reads (only to discover an error)?

Waiting too long when encountering an unreadable sector on a disk is really very annoying. (Especially if you are trying to read as much data as can be read from a disk with bad sectors, and do it ...
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0answers
32 views

Can ramdisk improve performance when stats show low wait and system cpu use?

I have jobs that do I/O of rates peaking around 200mb/s. On high load (over twice cpu cores) I tried to copy large file and got only few mb/s. Gathered dstat show single digits in wai and sys category ...
5
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2answers
88 views

How can I see i/o stats for a briefly running process?

For long running processes like init, I can do things like $ cat /proc/[pid]/io What can I do if I want to see stats for a briefly running process such as a command line utility like ls? I don't ...
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4answers
1k 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 ...
3
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1answer
83 views

Artificially prime buffer cache?

Is it beneficial to artificially prime the buffer cache when dealing with larger files? Here's a scenario: A large file needs to be processed, line by line. Conceptually, it is easy to parallelize ...
4
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1answer
74 views

Are writes to eventfd counted as io?

I am trying to reduce hard-disk activity on my system. Running iotop shows that Eclipse (the IDE, latest version (Luna)) is writing kilobytes of data every few seconds. So I ran strace on the eclipse ...
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32 views

Calculate Total disk i/o by a single process [duplicate]

I am looking for some tool that will dump total disk I/O by a single process after it ends. So far my finding is :- iotop= It shows i/o per process in real time but does not give total after process ...
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4answers
675 views

Utility to buffer an unbounded amount of data in a pipeline?

Is there a utility that I can stick in a pipeline to decouple read and write speeds? $ producer | buf | consumer Basically, I want a utility buf that reads its input as fast as possible, storing it ...
2
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0answers
309 views

`crontab -e` sometimes fails with “Creation of temporary crontab file failed”

From time to time crontab -e fails on me on a Ubuntu box. It is the same for all users including the root and crontab -eu <user> under the root. Goes like this on a regular basis, a success here ...
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970 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 ...
2
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1answer
84 views

I/O schedulers for normal harddisks

For me figuring out what is the best choice for I/O in kernel was a challenge. First I learned that it is subjective then it is depend upon the File-System you use. I know you should use No-op for ...
5
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2answers
872 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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3answers
107 views

Low level disk i/o on linux

Can a user level program do page level or block level I/O on SSDs? I've looked at disk devices, but am unsure if they provide this as they work only if the partition has a file system. UPDATE #1 I ...
0
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1answer
149 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 ...
2
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2answers
1k views

High Idle CPU / Low CPU Load average

After removing APC (alternative php cache), I noticed that there are less pagination access and less dirty pages but in the same time: High idle CPU Very low CPU load (relatively to the time before ...
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5answers
3k views

Why is iterating over a file twice faster than reading it into memory and computing twice?

I'm comparing the following tail -n 1000000 stdout.log | grep -c '"success": true' tail -n 1000000 stdout.log | grep -c '"success": false' with the following log=$(tail -n 1000000 stdout.log) echo ...
2
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3answers
115 views

Is it possible to generate a separate file list when creating a tarball?

When using tar for backups I'd like to create a separate list of the files that is included in the archive for storing alongside the backup tarball. I also want to be able to store the error messages ...
5
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5answers
433 views

performance monitoring

Is there some performace monitoring tool which would run in background gathering info about all system activity? Somethimes my system (Arch linux, 32 bit) slows down terribly and the top utility ...
3
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2answers
136 views

Monitor when read/write on metadata or mmaped files hit the disk

On a server hosting a wide range of websites, I often see IO becoming a bottleneck without being able to identify the processes responsible of IO operations with tools such as iotop, iostat or sar. I ...
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22 views

I2c with 16 bit addresses

So, i'm trying to interface with a device that has 16-bit addresses, and the master I'm using also supports this mode. However since this isn't standard I2C (should be 8-bit addresses) I haven't been ...
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2answers
32 views

How to know if io stream should stay open or close each time

I have a program that need to write in a file every second. I thought there is a too much overhead if I open and close the file each time. So I decided to keep open the file io stream. But I don't ...
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2answers
94 views

dd command: Finding read/write throughput of a flash/SD?

I am running petalinux from sd card. And trying to find data copying rate from Sd card and from QSPI flash that is there on the Xilinx Zynq board. As suggested here , I am doing like this: ...
2
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2answers
119 views

Tool to show PID and file I/O in realtime

I need to watch a program which modifies some files. I don't know which files the process is modifying_. So I'm looking for a tool that basically outputs a PID, and lista the files being ...
7
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3answers
538 views

Harddrive I/O per Pid

is there any way to see the disk I/O per pid/process ? Monitorix shows me the following and correct me if I´m wrong, but it looks like that the harddrive is slowing down the whole system: UPDATE #1 ...