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Questions tagged [io]

IO (or I/O) is an abbreviation for input/output, most commonly referring to disk input/output.

IO (or I/O) is an abbreviation for input/output, most commonly referring to disk input/output.

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Can anyone explain precisely what IOWait is?

As much as I have read about iowait, it is still mystery to me. I know it's the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also not sure, is why it so important? Can't the CPU…
Peter Krumins
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Are networks now faster than disks?

This is a software design question I used to work on the following rule for speed cache memory > memory > disk > network With each step being 5-10 times the previous step (e.g. cache memory is 10 times faster than main memory). Now, it seems that…
pm100
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How to check disk I/O utilization per process?

I'm having a problem with a Linux system and I have found sysstat and sar to report huge peaks of disk I/O, average service time as well as average wait time. How could I determine which process is causing these peaks the next time it happen? Is it…
Avada Kedavra
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Linux - How can I see what's waiting for disk IO

I have a server that has a really high load. Nothing is jumping out at me in terms of CPU usage, and it's not swapping. I think it's cause some processes are waiting for disk IO, and I want to see what's waiting. Is there any programme that'll show…
Amandasaurus
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5 answers

Measuring 'total bytes written' under Linux

We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article manufacturer's are reporting drive endurance in…
badnews
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5 answers

How to identify I/O bottlenecks on a Linux server?

How do you determine that the performance of your Linux server is I/O bound and, perhaps more importantly, what process or processes are casuing the problem?
cletus
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How can I monitor network I/O usage per process under Linux?

Such known tools like iftop/iptraf display network I/O per interface and per connection. Is there a way to see network I/O statistics per process?
Anonymous
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2 answers

kworker consuming +90% IO and zero disk write

this is a standard apache web server on AWS Linux AMI + EBS. We are noticing high load average (+8) and iotop -a shows: Total DISK READ: 0.00 B/s | Total DISK WRITE: 2.37 M/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND …
user2383712
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jbd2/dm-0-8 consuming all I/O

What is jbd2/dm-0-8 and why It is consuming all my I/O usage and causing I/O wait? Is there anyway to disable this? Bonnie++ results: http://pastebin.com/iQCWP1qp $ sudo hdparm -t /dev/sda1 /dev/sda1: Timing buffered disk reads: 108 MB in 3.02…
Super Mario
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Determining which process is causing heavy disk I/O?

I've seen this question: How to identify heavy write to disk? And I've used dstat and atop before...but they don't seem to pinpoint what process is causing disk I/O. For example, from dstat: dstat -ta --top-bio ----system----…
davr
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Is there a way to get Cache Hit/Miss ratios for block devices in Linux?

Is it possible to see in Linux how many read and write requests from user space end up causing cache hits and misses for block devices?
Kyle Brandt
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Why CPU spent time on IO(wa)?

I know wa (in top) measures the CPU time on waiting for I/O. Many articles say that. But I am confused that, based on 2 knowledge points: if a process uses a system call to read disk, the process is blocked. If a process is blocked, it is cannot be…
HUA Di
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Total I/O cost of a process

I know that iotop lets me measure the disk bandwidth used by any or all processes in real time. iotop -a measures the accumulated disk bandwidth, which is closer to what I want. However, when the process I run terminates, it disappears too soon in…
user308485
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Virtual machines and I/O heavy workload, is it ever sane?

I have seen on numerous virtualization services (Azure) and products (vmware,kvm,hyperv) I/O and system stalls under heavy I/O workload. My questions are: Is it ever sane to use a Virtualized solution when performing I/O heavy workloads? What are…
bryan hunt
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How do limit disc i/o during backup?

I have a cron that basically do a simple "tar zcf" in the night. The server has: 8 Cores - Intel(R) Xeon(R) CPU E5606 @ 2.13GHz 25GB RAM Ubuntu 12.04.2 LTS Hardware RAID 1 (LSI Logic / Symbios Logic MegaRAID SAS SMC2108) with two 2.728TB…
acemtp
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