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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.

401 questions
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How to keep md-raid from blocking IO?

I run a server with md-raid (software) level 1 (2 HDDs mirroring) and several different applications run on it. The problem arises when file-intensive jobs (e.g. extracting large archives) run while some users are also using realtime applications…
Cobra_Fast
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How I can reduce disk IO in MySQL 5.6.26?

I was using MySQL version 5.1.52 for my application but recently I have updated it to 5.6.26, but now I am facing very high disk IO. Following are system configuration: OS : Linux 2.6.39.4 RAM : 2GB Disk : 30GB Compact Flash. My O.S is same just…
purvesh pardeshi
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Long Response Times for Reads via FCoE

We're getting some intriguing performance with our new FCoE environment, and I was hoping that people could let me know if what we're seeing is expected behaviour. Our switching environment consists of 2 x Cisco Nexus 5672 switches, each having a…
Evan M.
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How to check what is causing performance issue

[Edit] This question is different than what is suggested by the moderator, I am trying to find out what could have caused the API to become slow because of the few lines of codes. I am not trying to do capacity planning as suggested by the…
forestclown
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How many milliseconds of await is considered to be high?

How many milliseconds of await is considered to be high? i have 800ms and 600ms iostat -x avg-cpu: %user %nice %system %iowait %steal %idle 1.28 0.00 0.22 0.90 0.00 97.60 Device: rrqm/s wrqm/s r/s w/s …
Gabriel Sousa
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CPU or network I/O bound?

I'm trying to find out whether my server is network IO bound or CPU bound. I did look at the output of some of the typical tools to check the current status of the system (output of iostat, sar and top below) but I'm not quite sure if my…
sme
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Get NewRelic to respect ionice'd processes

On our web server, we perform an incremental backup of our files every 4 hours using rsnapshot. To perform the actual copying of files, I've configured it to use a custom script, cp-nice that has the following contents: nice -n19 ionice -c3 cp…
rinogo
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Most side effect-free way to archive a large file while it is being modified

I am looking after an application that generates a large amount of data in a log file (about 5G a day) on a Red Hat server. This process runs for 24 hours during the week, so there is no point in the day when the file is not being modified, although…
notdazedbutconfused
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Redis parent process smashing disk despite appendfsync = no

We are seeing loads of IO from redis-server despite our save operations being set to occur once every 15 minutes only. The workload is a "full page cache"; we store blobs of compressed HTML. The HTML can be re-created on the fly if necessary, we…
Jon M
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Sustained io testing linux

I wish to hammer the io of some disks for an extended period of time and become aware whenever I can't read from a block (or some other symptom letting me know of an issue with backend storage). There are some benchmarking tools that write for a few…
derpy
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Does Linux, Apache HTTPD or PHP cache frequently / recently accessed files?

Let's say we have a simple index.php file that goes:
light
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File IO being slow

I've rented this root server with a RAID1 mdadm software raid setup. Using dd to benchmark the file IO speed it achieves 230MB/s write (default blocksize). Certain tasks such as mysql are way slower, though, using iotop it averages at about…
Sorunome
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What is the purpose of a ramdisk when fadvise exists?

My understanding is that fadvise will tell the system that the indicated files should be stored in the file system cache (RAM). What is the purpose of mounting a directory in a ramdisk when you can just fadvise --willneed the directory?
Philip
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Does AWS EC2 have secondary disks scattered across the cluster?

I am using AWS EC2 Linux m3.xlarge to run a program called "Smart Information Retrieval System" which performs many I/O operations to/from the disk. I have tried running the same program on my laptop and on a different cluster, and the performance…
Arturo
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What is the difference between truss -D and truss -E?

I am currently analyzing a command on Solaris that reads from a file and has very low performance. The truss -D commands shows me read system calls taking up to 0.03 seconds, but when I use truss -E, they are always either 0.0000 or 0.0001 (two…
dokaspar
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