Tagged Questions

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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3
votes
1answer
54 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 ...
2
votes
0answers
31 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 ...
1
vote
1answer
73 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. ...
0
votes
1answer
192 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
votes
1answer
79 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 ...
0
votes
2answers
43 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
63 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
54 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
72 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 ...
1
vote
1answer
36 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 ...
1
vote
1answer
83 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 ...
2
votes
0answers
119 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 ...
0
votes
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 ...
2
votes
1answer
77 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 ...
1
vote
1answer
42 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 ...
0
votes
0answers
26 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
votes
2answers
75 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
votes
1answer
73 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 ...
6
votes
2answers
183 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 ...
0
votes
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
votes
1answer
67 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
votes
0answers
226 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
votes
1answer
72 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
vote
3answers
90 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
votes
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 ...
2
votes
3answers
103 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
votes
0answers
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 ...
3
votes
2answers
104 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 ...
24
votes
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 ...
0
votes
2answers
30 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
636 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
votes
2answers
108 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 ...
1
vote
2answers
84 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
votes
1answer
276 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
votes
3answers
438 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
votes
0answers
206 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
votes
1answer
64 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
votes
1answer
44 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. $ ...
5
votes
3answers
396 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: ...
5
votes
4answers
1k 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
votes
0answers
130 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
votes
1answer
960 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 ...
3
votes
3answers
769 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
222 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. ...
1
vote
0answers
161 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 ...
0
votes
0answers
107 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 ...
1
vote
3answers
375 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. ...
1
vote
1answer
5k 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 ...
10
votes
1answer
155 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
vote
1answer
66 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 ...