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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26 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 ...
3
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1answer
55 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 ...
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0answers
22 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
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 ...
4
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1answer
45 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 ...
2
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0answers
66 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 ...
2
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1answer
52 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 ...
1
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3answers
51 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 ...
2
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2answers
162 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 ...
2
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3answers
79 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 ...
0
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0answers
18 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 ...
3
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2answers
60 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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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 ...
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2answers
25 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 ...
2
votes
1answer
303 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 ...
2
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2answers
99 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 ...
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2answers
67 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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1answer
118 views

What is the recommended way of setting a default IO scheduler on Linux?

I would like deadline to be the default IO scheduler for my system, and I don't want to lose that config when I reboot. What is the proper way of doing that? (I'm using Debian) Some hints: have a ...
7
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3answers
261 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 ...
3
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0answers
90 views

Unable to close a Luks partition

For backup purposes, I have "snapshotted" a LVM partition. This partition was crypted so I have opened this Luks partition (snapshot) in order to do my backup. The problem is that I have forgotten to ...
2
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1answer
46 views

How to customize or reprogram function of specific keys on my keyboard and the LED on my laptop

When I disable bluetooth on my laptop, the light does not go off and the blinking of the Wi-Fi LED is starting to bother me. Since I sometimes use my laptop in a poor lighting condition an illuminated ...
0
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1answer
41 views

Copy a file that is in the middle of being written

I have a program that writes to the standard output. It does not write all info at once, it does computation and then writes new bits. The output of the program is being stored in a file. $ ...
4
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3answers
201 views

Poor IO due to LUKS/Software RAID/LVM ordering?

I'm trying to determine if I should re-setup my RAID array due to poor IO performance. First off, the system: i7 920 4 4TB WD 5400 Green drives CentOS 6.3 host Secondly, the disk setup: ...
3
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3answers
435 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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0answers
105 views

jbd2 journal constant i/o

iotop reports a constant i/o about 3% of [jbd2/vda1-8], I think this is the journal manager for ext4. my fstab is: UUID=X / ext4 defaults,noatime,nodiratime 1 1 tmpfs /dev/shm ...
4
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1answer
523 views

how can I retrieve disk IO utilization in percents on HP-UX

I need to collect data about disk utilization for selected disks. I can use glance-plus monitoring tool to display the current data in percents (it looks similar to top), but I need to collect these ...
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3answers
419 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 ...
4
votes
2answers
163 views

why does blktrace only write blocks of 8?

I want to understand the I/O pattern a database is writing to disk to decide how many disks to use for best performance. To analyse the I/O pattern I want to use blktrace and I have to grok it first. ...
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0answers
143 views

IOMMU causing freezes, disabling causes USB to not work

I'm somewhat new to linux, but I'm running a Xubuntu machine that I recently built. Since I started it up, I had noticed frequent freezes, where both the screen (if plugged in) and any SSH session ...
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0answers
77 views

Is swapping the cause of high IO on my box?

I'm running a LAMP stack on an Amazon EC2 micro instance with 616 MB of memory. This seems sufficient to be able to run a few small websites with Apache, MySQL and PHP. I have one Wordpress site ...
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3answers
288 views

Amazon EC2 micro instance large number of IO requests

I'm trying to understand why I have a huge number of EBS IO request on my Amazon EC2 micro instance. I launched the instance roughly 6 days ago and has racked up over 4 million IO requests so far. ...
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1answer
3k views

iostat: await vs. svctm

In the iostat manpage I have found these two similar columns: await The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by ...
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1answer
154 views

Moving a file to a file that is being read

When a file is moved and the destination file already exists and is currently being read, will the operation succeed? Will it depend on how long the reading operation on the destination file lasts?
1
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1answer
62 views

I/O brings a machine to its knees [closed]

Why, on every Linux I've used, when a program is really I/O bound, it bogs the machine down? It just happened when I (accidentally) tried to make gcc compile a (valid!) 50Mb C file. GCC was so I/O ...
3
votes
3answers
75 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 ...
0
votes
1answer
98 views

best programming language for I/O intensive tasks [closed]

I need to process "big data" (nearly 1TB which can be partitioned into smaller chunks). Consider several programming languages (Java, Python, C++, Perl) and other scripting options (Perl, awk, sed, ...
5
votes
1answer
270 views

`unbuffer` or `stdbuf` for removing stdout buffering?

Is there a difference between unbuffer(1) and stdbuf(1)? From what I gather, unbuffer makes more than the "best effort" of calling the libc function set(X)buf at the beginning, and then letting things ...
1
vote
2answers
315 views

How I/O channels are implemented in Linux kernel?

stdin, stdout, stderr are some integers that index into a data structure which 'knows' which I/O channels are to be used for the process. I understand this data structure is unique to every process. ...
4
votes
1answer
153 views

Execution time and resources after processes that has been running for so long

This might be a basic question, but I am getting hard time finding an answer to it. I am using RHEL6. After running any process that takes significant cpu time, I get a line that tells (I guess) the ...
3
votes
2answers
431 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
60 views

Getting IO privileges in Linux

I have installed flashrom software. When i try to run sudo flashrom command it gives me "Could not get I/O privileges (Operation not permitted). You need to be root" error. Also I tried su command to ...
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0answers
140 views

How different is I/O handling of hard disk in AIX and Redhat Linux?

I am running a hadoop I/O workload in redhat linux and have ran that in IBM AIX as well with same underlying hardware, disk and disk configuration. With the default settings on the os redhat linux is ...
0
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2answers
129 views

IO utilization for /dev/null redirection?

I always use nohup to start my system. However, the output to nohup is so big that I'm thinking to redirect it to /dev/null. My concern is, will redirecting to /dev/null also incur some I/O operations ...
1
vote
1answer
431 views

How to measure total disk I/O per hour

I have a cloud server were we get billed also for disk IO usage. Here is an example from the stats: 04/Sep/2013 07:24:19 04/Sep/2013 08:24:19 0,5 GB / 1 vCPU (0,08 Kr. per hour): Charge for ...
2
votes
1answer
69 views

Why don't I see a file being copied right away with ls?

Is it due to the buffering in memory? I did cp /network/large_file . & and I kept doing ls -lh to monitor progress, but the file didn't appear until it was about 400MB. Linux 2.6 kernel, Bash 4, ...
4
votes
1answer
220 views

fstrim and iostat

I have a new samsung ssd in my new notebook. I tuned up everything to avoid writings in the disk (firefox profiles and /var/log in memory), I'm using a ext4 fs with relatime and I use fstrim once a ...
1
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1answer
80 views

Strange problem with IO or file system or what?

On a SLES 11 SP2 32-bit system I'm seeing a strange problem. It's as if the OS can not open a file from the beginning of the file. Say I have a file that is 200 lines. If I cat or more or vi the ...
14
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3answers
2k views

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
417 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
122 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 ...