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Questions tagged [disk-io]

Input/Output operations involving local persistent storage.

Common topics using this tag:

  • I/O-Bounded operations
  • General interaction with local storage

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138 questions
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Readahead effect on Linux fread()

I have a problem with readahead performance of a large binary file. My strategy is Read a fixed size chunk from the large binary file with fread(). (e.g. 10MB) Sleep for n milliseconds with usleep() just for readahead performance measuring. Repeat…
Yuf
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Can anyone recommend disk I/O benchmarking software for Windows?

I want to test the performance of a filesystem under different conditions. Specifically I want to test the performance of Windows virtual machines without compression and with compression both on "normal harddisk" and on USB-disk as it would be…
Tedd Hansen
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Postgres create/restore taking lot of time on amazon ec2

I have a amazon ec2 instance(SAY S1)(4core-7GB memory) using Ubuntu 12.04, which is running my web app with postgresql 9.1. All the postgres data is stored on to a different ssd volume(not root) of 100 GB. (Write now its currently 26% full only ) .…
Ankit Kulkarni
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How to Safely and Transactionally Replace a File on Linux?

The most naive, worst way I can think of to replace the contents of a file is: f = open('file.txt', 'w') f.write('stuff') f.close() Obviously, if that operation fails at some point before closing, you lose the contents of the original file while…
dave mankoff
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Windows 10 docker-compose takes 100% disk usage

Docker is very slow on windows 10. I followed a lot of the tasks to make the index not run on the folder and tried to speed things up. The process appears to take up 100% of the CPU, which is fine, but also 100%+ of the disk IO and that is a huge…
Ben Holland
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SCAN and CSCAN algorithm

I am having hard time understanding the working of SCAN and CSCAN algorithm of disk scheduling.I understood FCFS,Closest Cylinder Next but heard that SCAN resembles elevator mechanism and got confused. My book says that for the incoming order :[10…
Khan
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Parallel Disk I/O

I have several logfiles that I would like to read. Without loss of generality, let's say the logfile processing is done as follows: def process(infilepath): answer = 0 with open (infilepath) as infile: for line in infile: …
inspectorG4dget
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Why is IO 99.99 % even though the Disk Read And write seems to be very small

One of our Kafka brokers had a very high load average (about 8 on average) in an 8 core machine. Although this should be okay but our cluster still seems to be facing problems and producers were failing to flush messages at the usual pace. Upon…
Ankur rana
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Are native OS operations optimized on a per-process basis while writing same file?

I'm trying to understand some internal details of file writing operation done through managed code in C#. Let's say I write below piece of code to write some content into a log file: using System.IO; public void Log(string logMessage, LogLevel…
RBT
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Unexpected behavior of sstableLoader

I'm working on two different machines and both have different hard disk storage and different cassandra version. machine 1 SSD hard disk, Cassandra 2.1.13 machine 2 HDD hard disk, Cassandra 2.1.3 Now I transferred data of one CF from machine 2 to…
Anonymous
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Do named fifo pipes use disk writes and reads ?

I want to parse MySQL general log and store that information on another server. I was wondering if it would have a performance increase to have MySQL write its log to a Linux named pipe FIFO instead of just moving the log file and then parsing…
MrNemus
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Webapp: Mysql: Row level security. Pro/cons? A better way to do this?

I am trying to emulate row level security on a webapp I am developing using MySQL. Using this method: Creating a database with the the required tables where the data pertaining to all the users will be stored with proper indexing of columns of the…
ThinkingMonkey
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why direct io much slower than non-direct io on SSD(performance measured after system cache cleared)?

I'm new to optimizing disk IO performance. I compared the performance of reading from file with or without direct IO enabled. The chunk size is 512KiB. As Direct IO reads data from disk directly to buffer in user space, I think Direct IO should be…
lei hu
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Is there a utility for the Mac (OS X Lion) to monitor cpu and disk usage per process over a period of time?

I am looking for a good utility running on OS X Lion that would give me a per process summary of CPU usage and Disk I/Os. I don't want to monitor the instant usage, but to find out the average CPU and disk usage over a period of time (like a day of…
Jean-François Beauchamp
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Does a SQL Server Update statement for nvarchar overwrite the same address on disk if the new value is the same size? (Microsoft SQL Server)

Is it possible to overwrite the same disk address on a TSQL update statement? A use case would be preventing recovery of the original text on disk for security or anonymity reasons. CREATE TABLE Test( Id int, Message nvarchar(1000)) GO INSERT…
Francisco d'Anconia
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