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Deploy application with kubernetes statefulset

StatefulSet is the workload API object used to manage stateful applications. Like a Deployment, a StatefulSet manages Pods that are based on an identical container spec. Unlike a Deployment, a Sta...

Docker-based fio benchmarking - Part Two

In this article, we will build a docker image which is based on python versioned alpine Linux. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer...

Docker-based fio benchmarking - Part One

Why Docker-based fio benchmarking fio is a flexible I/O tester which generates I/O and measure I/O performance on the target storage system. In the case we want to run the fio workload on the clou...

Concepts you should know

Data structure Bloom filter A Bloom filter is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set. For example, checking availability of us...

Storage concepts you should know

Object Storage Object storage, also known as object-based storage, is a strategy that manages and manipulates data storage as distinct units, called objects. These objects are kept in a single sto...

Network concepts you should know

IP address Networking is about one computer sending a message to another computer. This message is called packet in the IP world. It is just like a postcard in the postal service. The postal servi...

Database concepts you should know

SQL vs. NoSQL Source Benefits of NoSQL databases NoSQL databases offer many benefits over relational databases. NoSQL databases have flexible data models, scale horizontally, have incredibly f...

Distributed system concepts you should know

This post contains basic explanations for concepts you should know related to distributed system. API and REST API Application Programming Interface, abbreviated as API, enables connection betwee...

Estimate the scale of the system

It is always a good idea to estimate the scale of the system as it help reflect if the designed system could fulfill the functional requirements. The requirements might include: Number of users...

What is high availability

What is high availability? High availability refers to a system or component that is operational without interruption for long periods of time. High availability is measured as a percentage, with...

Latency numbers

Latency Comparison Numbers (~2012) Conclusion Disk is much slower than the memory Avoid the disk seek if possible Compressing data is worth to consider before sending over network It t...

Data volume units

Data volumes The volume of data in a single file or file system can be described by a unit called a byte. However, data volumes can become very large when dealing with Earth satellite data. Below ...

Using node selector to assign virtual mahcines to a node

In some circumstances, we want to control which node the virtual machine or pod deploys to. The node selector can be used to assign virtual machine or pod to a node. Add label to a node The label...

Understanding thin provisioning volume and snapshot

Thin provisioning volume Logical volume can be thinly provisioned. It allows storage administrator to overcommit the physical storage. In other words, it’s possible to create a logical volume whic...

Using virtctl to access virtual machine in Kubernetes

Install the virtctl client tool Basic VirtualMachineInstance operations can be performed with the stock kubectl utility. However, the virtctl binary utility is required to use advanced features su...

How to configure SAR data collection on RHEL8

On RHEL8, it uses systemd instead of cron jobs to manage SAR data collection service. Run the following command to check if the SAR data collection is started. [root@h04-11 ~]# cat /etc/redhat-re...

Solve LeetCode problems in Visual Studio Code

Install the leetcode extension in VS Code Login to LeetCode endpoint with cookie Login to leetcode from Google Chrome In Chrome, Inspect -> Network -> Fetch/XHR Click on any button...

libaio init failed due to resource temporarily unavailable

Issue Description $ sudo fio --blocksize=64k --directory=/mnt/bench1 --filename=testfile --ioengine=libaio --readwrite=randread --size=10G --name=test --numjobs=512 --group_reporting --direct=1 --...

How to uninstall ceph storage cluster

Check the pools, images and OSDs [ceph: root@host1 /]$ ceph osd tree ID CLASS WEIGHT TYPE NAME STATUS REWEIGHT PRI-AFF -1 83.83411 root default -3 27.94470 ...

fio benchmark on multiple files

fio directory and filename options To run fio benchmark on multiple files or deives, we should understand the following fio options. directory=str Prefix filenames with this director...