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journalctl - Query the systemd journal

journalctl may be used to query the contents of the systemd journal as written by systemd-journald.service. If called without parameters, it will show the full contents of the journal, starting wi...

Flame graph - A visualization for profiling and debugging

Flame graphs can be generated from the output of many different software profilers, including profiles for different resources and event types. The article written by Brendan Gregg describes how th...

Deploy kubernetes statefulset with affinity

Here is an example to demonstrate how to assign statefulset and pod to the target worker node. affinity helps define which node will be assigned for the pod by using the node labels. $ kubectl ge...

A six-step framework to tackle any system design question

Introduction In the book of System Design Interview by Lewis C. Lin, a six-step framework called PEDALS is introduced to help answer any system design question. PEDALS stand for: Process requ...

The complete guide to System Design in 2022

The complete guide to System Design in 2022 covers: What is System Design? System Design fundamentals Horizontal and vertical scaling Microservices Proxy servers ...

Understanding RPO and RTO

The disasters could occur unexpectedly and it could take down the whole data center in an application region. In the real world, a well designed disaster recovery solution would help restore the ap...

Understanding the Linux inodes

Linux makes a clear distinction between the contents of a file and the information about a file. All information needed by the filesystem to handle a file is included in a data structure called an ...

Lambda architecture in big data system

What is Lambda Architecture When working with very large data sets, it can take a long time to run the sort of queries that clients need. These queries can’t be performed in real time, and often r...

Understanding MapReduce with an example

What is MapReduce MapReduce is a programming framework that allows us to perform distributed and parallel processing on large data sets in a distributed environment. MapReduce consists of tw...

AngularJS table creation for dynamic number of columns

<head> <link href="css/bootstrap.min.css" rel="stylesheet"> <script src="js/bootstrap.bundle.min.js"></script> <script src="js/angular.min.js"></script&...

Hide and display html elements

<body ng-app="myapp"> <div class="container-fluid" ng-controller="myctrl"> <ul class="nav nav-tabs" id="myTab" role="tablist" style="display:flex"> <li ...

Access a sharedv4 volume outside of a Portwrox cluster

To access a sharedv4 volume outside of the Portworx cluster, add the allow_ips label to the volume you wish to export, specifying a semi-colon separated list of IP addresses of non-Portworx nodes y...

Using iperf to measure the network bandwidth

iPerf is a tool for measurements of the maximum achievable bandwidth on IP network. The following iperf option can be used on the client side to saturate the network bandwidth if single client thre...

How to deploy MySQL and phpMyAdmin with Docker

Create the MySQL docker container $ docker pull mysql/mysql-server:5.7 $ docker run -d --name=mysqldb -e MYSQL_ROOT_HOST=% -e MYSQL_ROOT_PASSWORD=password -e MYSQL_DATABASE=perfdb -v /var/lib/osd/...

What is Performance Engineering

Useful tools in Linux operating system

Performance tools vmstat iostat ifstat netstat nfsstat mpstat nstat dstat sar iftop pidstat xosview Benchmark tools fio iozone iperf netperf vdbench sysben...

OpenZFS - A pooled storage file system

OpenZFS The OpenZFS project is an open source derivative of the Oracle ZFS project. OpenZFS is an outstanding storage platform that encompasses the functionality of traditional filesystems, volume...

Fio initial write, overwrite and append write

In this post, we try to study how the overwrite and file_append options work in fio benchmark. overwrite and file_append options overwrite=bool If true, writes to a file will always overw...

Fio fsync, end_fsync, fdatasync and sync

Intro to fsync, end_fsync, fdatasync and sync fsync=int If writing to a file, issue an fsync(2) (or its equivalent) of the dirty data for every number of blocks given. For example, if you ...

Scale a system to support millions of users

Start from single server Building a large scale system is not one time effort, it should be an iterative process as the user workload increases. The journey could just start with single server and...