DEV Community: technonotes-hacker

Promotion - Oracle ASM

technonotes-hacker — Sun, 11 Oct 2026 15:59:04 +0000

Oracle Automatic Storage Management (ASM) is a built-in volume manager and file system for Oracle Databases that simplifies storage administration.
Its a Volume Manager
What will the Volume Manager will do ? and what do you mean by Volume ?

5TB Big Data , you need to store this --> In storage every single disc is having only 1TB. 
5 Hard Disc Needed. 
Multiple Disc into single disc to the outside world.
1 Volume can have 1 Physical Hard Disc or Multiple Hard Disc.

These storage software will take care the Volume Manager also.
If we assign Multiple disc to ASM , ASM can handle the disc , ASM add the disc from the Volume , Remove the disc from the volume , ASM can perform the redundancy of the storage, ASM can perform the Load Balancing inside the disc.
ASM provides the Volume Manager layer which is needed by every storage software.
ASM also acts as a File System.

What you mean by File System ?

Its a storage area.
File System is basically a STORAGE.
File System as Storage area for Oracle Database.

Oracle Clusterware

You can use it for Cluster Management not only for Oracle but for any other infrastructure.
It can be installed to manage the cluster , it doesnt mean that you need to have only Oracle RAC.

Oracle ASM --> its is File System Storage only for Oracle RAC / Standalone Database. Its not supported for others.

What type of File can store in ASM ?

RMAN Backup
Flash Back Log
Export Import Files
Expect PFILE , all are in Binary Mode. So all files can be stored in ASM.

DiskGroups in ASM

Collection of disks which make a volume ( diskgroups )
Diskgroup is nothing but Volume.
Diskgroups --> Collection of disk at the OS level.
You can assign / must assign a name to diskgroup. Eg., ASM1 /dev/sdc1 --> The ASM1 name will be assiged to the physical disc.
Minimum ASM Structure defined by Oracle is --> 3 Discgroups for basic Oracle RAC configuration.

CRS Diskgroups --> To store cluster related files
DATA Diskgroups --> To store database files like datafiles etc
FRA Diskgroups --> To store FRA files

FRA --> Fast Recovery Area

Where we named ASM1 ? At what place ?

When we installed the ASM Binary , Post ASM binary , we had issued a command " Oracle ASM CREATE DISC ".

What is DISkS ?

Physical HDD Storage
One HDD can't belong to two discgroups
But Multiple HDD can be belonged to one single discgroup.
Types of storage considered for ASM:

Complete HDD partition.
Multiple HDD Partitions assigned to single ASM disks
NFS
LUNs allocated from Storage. Oracle doesn't recommend this ? Why ?

ASM is already a Volume Manager, so when allocate LUNs from the storage server , storage software is again a Volume Manager. Two Volume Manager are not recommended for storage of data. Because you will have Redundancy of Volume Manager.

Eg., for point 2

/dev/sdc
/dev/sdc1 --> ASM2 ( These are only disk )
/dev/sdc2 --> ASM3
/dev/sdc8 --> ASM7

ASM2 is a single disk , can be assigned to one diskgroup. But ASM2 can't be assigned to Multiple Diskgroups.

1 single diskgroup can have multiple disk , it means , single diskgroup can have ASM2 , ASM3 .
For ASM1 , I can add --> ASM1 /dev/sdc1 + /dev/sdd1 + ..
These disk will have datafile.

Lets get inside the ASM Instance

What is Oracle ASM Instance on STANDALONE DATABASE?

Its built on same technology as of database instance.
SGA + BG Processes ( BackGround )
No Redo Logs
Its just a mediator between Oracle Instance and the Storage Disc.
Its very small when compared to Oracle Database Instance as it performs very small task.
Its smaller in size when compared to DB instance.
where is Oracle ASM installed ? Oracle ASM is installed in GRID_HOME. ASM binary are installed under GRID HOME.
What exactly stored ? what is the metadata inside the ASM ? --> ASM manages the exact metadata of the disk group and provide file layout to Oracle Instance.
ASM instance is like a mediator between Storage ( diskgroup ) and Oracle Instance.
Every single machine as one ASM instance running on it.
3 DB instance on a single machine ==> 1 ASM instance shared by all the DB instances.

What is Oracle ASM Instance on RAC DATABASE?

Every single machine / node has one ASM instance running on it.

Oracle ASM Instance Failure

If the Oracle ASM fails on one node --> what will happen ? --> what happens to the Oracle DB instance ? or If the Oracle Database is running and suddenly Datafiles are deleted , what will happen ? DB instance FAILS. Same DB Instance also fails if ASM fails. ( DB instance will also FAIL )
Can I stop the ASM instance when DB is up and running ? ( Important Interview Question ) ---> Stop all the DBs instance accessing the ASM before stopping the ASM instances. This is the procedure.
From 12c RAC --> ASM Instance Fail over was introduced --> Oracle ASM Flex Cluster , need to be enabled.
what the ASM flex Cluster will do ? --> If the ASM in node 1 fails , then it communicates to ASM in node 2 and then access the shared location.

This is only available only from Oracle RAC 12c.
This is like High Availability.

ASM Mirroring & Failure Group

Mirroring is like Maintaining a copy of your data.
Its like "A diskgroup is mirrored to another diskgroup".
Oracle ASM itself provides the redunduncy.
You have to mention the redundancy at the time of disk group creation.
Once done , it can't be changed.
Types of Redundancy in ASM :

Normal --> 2 way redundancy --> 2 failure groups , Max you can have 3 Failure groups.
High --> 3 way redundancy --> 3 failure groups , Max you can have 5 Failure groups.
External --> No ASM level redundancy or you can have external Softwares for redundancy.

What is Failure Groups ?

One Single Failure Group is one Single redundant Copy.
To increase the redundancy , we can have multiple Failure groups.

Failure Group are defined while creating the disk group.
Failure Group is nothing but the redunduncy , no of failure group is nothing but the level of redunduncy.

ASM Adminstrator

ASM needs the Utility to administor.
SQLPLus ( How ? because ASM instance is like Oracle DB instance , so SQLPlus can be used )
ASMCMD --> ASM command mode
ASMCA --> ASM configuration ASSISTANCE --> its like GUI ( All things can be performed , even the upgrade of ASM ).
These are the Utility used. But these are only for STANDALONE DB.
What about RAC based Oracle Instance ? For Multiple ASM , then SRVCTL --> Clusterware Level Utility which allows you to administer all ASM Resources.

Note

DiskGroups as Table space
Disks --> is a Datafile.
In a tablespace can have multiple datafile. But single datafile can't be assigned to two tablespace.
SGA --> System Global Area
CRS --> Cluster Ready Services
LUNs --> Logical Unit Numbers
Database backup is taken by RMAN. ASM will allocate the channel to the diskgroup. No ASM comes inbetween for backup . RMAN directly write into the ASM diskgroup. No over head on the ASM instance.
When you take RMAN backup for OS level disk , does it give over head to the OS system ? Not really . Same , if you allocate channels to ASM diskgroup , RMAN will continur to write and ASM instance continue to perform until the diskgroup is full or ...
If you talk about Volume Manager --> Stripping , Mirroring , Load Balancing --> Everything is supported by Oracle ASM.
Irrespect of Database instance in a single node , only one ASM will be running for each node. That is the benefit .
Mostly EXTERNAL will be configured , as they will allow the storage team at HARD DISK level.
SRVCTL --> Server Control

Promotion - CertIn

technonotes-hacker — Sun, 11 Oct 2026 10:55:13 +0000

Indian Computer Emergency Response Team ( CertIn )
Its pivotal organization formed by Ministry of Electronics and Information Technology 2004.
Effective response to Cyber Incidents.

Role

Safeguard systems and network from:

Cyber threats
Including Malware , Hacking and Data Breaches

Its key role is to monitor and analyse cyber threats and Vulnerabilities.
Source : Government Agencies , Private Sector Organization , International Partners which helps to identify emerging threats and trends.
The advisories and alerts are circulated amoung stakeholders.
It also conducts awareness program.
Fostering a culture of Cyber Security AWARENESS.
Aims to empower individuals and Oraganization to protect themselves against Cyber threats.
The Role of CERT-In in ensuring cyber security is becoming more critical day-by-day.

Technical Guidelines on | SBOM | QBOM & CBOM | AIBOM | HBOM |

SBOM

Software Bill of Materials
A complete inventory of software components used in an application.
Includes:

Libraries (open source + proprietary)
Versions
Licenses
Dependencies
Vulnerability mapping

AIBOM

AI Bill of Materials.
It includes servers, sensors, and GPUs. Also AI models , frameworks ,and development tools.
Inventory of all AI‑model components, mandatory for AI systems.

Model name, type, version
Training dataset sources
Algorithms & architecture (LLM, CNN, etc.)
Open‑source AI components
External integrations
Governance approvals (MANDATORY per CERT‑In)

Benefits of AIBOM

Minimum Elements Required

Recommendation & Best Practices

The format for generating AIBOM for AI solutions should adhere to established standards, such as Software Package Data eXchange (SPDX) or CycloneDX, ensuring compatibility and uniformity across the industry.
The AI developer/integrator organization that supplies AI solutions to government and public sector organizations should develop a Vulnerability Exploitability eXchange (VEX) for AI models after a vulnerability or security issue is discovered.

HBOM

Hardware Bill of Materials
Inventory of hardware components supporting the application.

Servers
Network devices
Storage systems
Firmware versions
End‑of‑life/End‑of‑support status

CBOM

Configuration Bill of Materials
Inventory of configuration elements that define how the system is deployed.

Config files
Environment variables
Parameter sets
Network config (ports, protocols, IPs)
Deployment descriptors

QBOM

Cloud Bill of Materials
QBOM is referenced alongside CBOM in the CERT‑In document.
A structured inventory of all cloud components used by an application.

Cloud services (AWS, Azure, GCP, etc.)
Compute resources (VMs, containers)
Storage buckets / databases
Identity & access configurations
External APIs hosted on cloud

Notes

Pivotal --> extremely important or central because everything else depends on it.
foster --> to help or encourage the development of something (especially feelings or ideas).

Kubernetes - Day - 09 - Docker Quiz

technonotes-hacker — Sun, 11 Oct 2026 10:05:05 +0000

Just for first time --> docker run hello-world --> Docker can't find the image locally, so it pulls it from Docker Hub --> With no image on your machine, docker run pulls it from the registry, then creates and starts the container.

time docker run --rm alpine echo "hi" --> Run this command twice --> the second run much faster? --> The image was already downloaded on the first run. --> The first run includes pulling the alpine image. After that, starting the container is just starting a process.

docker run --rm alpine echo hi --> Removes the container automatically when it exits.

Which registry does Docker use when you don't name one? --> Docker Hub (docker.io)

Which command lists images on your machine? --> docker images

What problem does Docker mainly solve? --> "It works on my machine": packaging an app with everything it needs so it runs the same everywhere --> An image carries the app plus its libraries and settings, so dev, test and production run the same thing.

What do all containers on one host share? --> The host's Linux kernel. --> Containers are isolated processes on the host. Each gets its own view of files and processes, but they all use the host's kernel.

Why does a VM usually take longer to start than a container? --> A VM boots a complete operating system; a container just starts a process. --> A VM is a whole pretend computer with its own kernel. A container is a normal process with a private view.

Which program lets one physical server run several virtual machines? --> A hypervisor (KVM, VMware, VirtualBox)

An image is to a container as… --> a recipe is to a cooked dish (or a class to an object) --> One image can start many containers, just like one recipe can feed many plates.

Why does Docker Desktop run a small Linux VM on Windows and macOS? --> Linux containers need a Linux kernel, and Windows/macOS don't provide one.

Which statements about containers are true? (Pick all that apply.) --> They usually start in seconds or less , Their images are usually megabytes, not gigabytes & One machine can run many of them --> Containers are light because they skip the extra OS. No boot, no full OS image.

Kubernetes - A Complete Guide in Tamil - 1

technonotes-hacker — Sun, 11 Oct 2026 07:26:24 +0000

helmsman
A helmsman is a person who physically steers a ship, boat, sailboat, submarine, airship, or spacecraft.

K8s
Most popular for managing the container.
Open source container orchestration platform.
orchestration --> Management of container.
Automate --> scale up & scale down , Deployment process.
Load Balacing

History

Developed by Google - 2014
CNCF --> Managing the k8s ( CNCF acquried ).
Kubernetes a greek word for helmsman.
7 spokes in k8s represents 7 founders.

Why we need k8s ?

To update all the container at a time with docker is a challange or complex process.
Container should not go down ( maintaince ).
If container fails , it needs to restart by itself.
Production Challenges : Manual scaling , HA & Networking along with storage.

K8s

All the above will be automated by KUBERNETES.
Automating deployment & scaling.
Self-healing.
LB
Managing storage.
Its like Swiggy Eg., Order FOOD and just relax . Swiggy will take care everything.

To host the application inside the containers.
We can't directly work with container , here its called PODS.
Pods will run on worker nodes.

Docker Swarm vs K8s

Both are event organiser.
Docker Swarm contains --> Cluster --> Cluster contains --> Nodes --> Nodes containes --> Containers --> Containers contain APPs.
K8s contains --> Cluster --> Cluster contains --> Nodes --> Nodes --> Nodes containes --> PODS --> PODS contain --> Containers contain APPs.

Docker Swarm --> Small scale events. Eg., Common wealth
K8s --> Large scale events. Eg., Olympics

Cluster

Cluster is a group of servers or virtual machine.
Any cluster contains

Master Node / Control Plane
Worker Nodes / Data Plane

Control Plane

Its like a director
Manage the scheduling , scaling & Monitoring.
Control Plane is like டைரக்டர் சங்கர். Control Plane எல்லாத்தையும் பாத்துப்பார்.

Worker Nodes / Data Plane

Its like actors
Follow the instruction of control plane and ensure the task is executed.
Each nodes will have containers inside.
The actual work will happen inside the worker node.
Each node runs containers inside PODS.
Worker Nodes is like ACTOR ரஜினிகாந்த் மாதிரி டைரக்டர் என்ன சொல்றாரோ அதை தான் கேட்கணும். Implementation இவர்தான்.

k8s Architecture

Each worker node containes:

Kubelet
Kube-Proxy

CLI --> Command Line Interphase
Kubectl --> With this only we are going to communicate with KUBERNETES.

How deployment Happens in K8s ?

You can't interact with WORKER NODE directly.
Anything you need to do in K8S means , you need to do with Control plane only.
You want to create a POD ? Inside the POD , you want to deploy a Application.
Now the user request will go to API Server and the API Server will store the request to etcd.
etcd --> Store the request in this and its a internal datasource of K8S.
Now Scheduler will always check the etcd , is there any request available.
Scheduler found one request that " someone trying to deploy the application ".
Scheduler will decide , in which WORKER NODE it needs to deployed.
How the Scheduler decides which worker node ? --> Scheduler will have a information of the WORKER NODE. ( storage , pods are running already , CPU ) will be assessed by the scheduler.
How Scheduler knows all the details of the worker node ? There will be worker node agent called --> KUBELET.
KUBELET role is to gather WORKER NODE information , so its called WORKER NODE AGENT. Which as all the informatio n related to the worker node and send the information to the Scheduler .
Scheduler will decide in which worker node it should be scheduled. thats it.
Who is the actuall one to deploy ? Controller-Manager.
Kube-Proxy is the network interphase between Control plane and worker node and between pods.
Kube-Proxy is a Network element of K8S Cluster --> Container Network Interphase --> CNI.
CNI is a plugin.
CNI will take care

Communication smoothly happens between Worker node and Control plane.
Control Plane and worker nodes.
Pods running in the same container.
Pods which are runninhg in same worker node.
Poda which are running different worker nodes.

Inside Woker Nodes , you will have CRI --> Container Runtime Interphase.
CRI --> is nothing but --> DOCKER.
CRI will help to create the pods and inside the pods , container will be availble.

All these will happen in FACTION OF SECS.

Types of K8S Cluster

Self Managed Cluster

Minikube --> Single node cluster
_Kubeadm _--> Multi Node Cluster --> Manual Maintainence.
Kops--> Multi Node Cluster --> Manual Maintainence.
KinD --> Multi Node Cluster --> Manual Maintainence. ( Kubernetes in Docker ) --> Kubernetes can also be maintained in Docker.
rancher --> Self Managed.

Cloud Managed K8S Cluster

AWS --> EKS --> Elastic Kubernetes Service
Azure --> AKS --> Azure Kubernetes Service
GCP --> Google Kubernetes Engine ( GKE )

Methods of creating Cluster

Direct Console
CLI --> Command Line Interphase
Manifest file --> Configuration file
Terraform

Billing of K8S

0.10$ per hour --> https://aws.amazon.com/eks/pricing/?trk=d04c06f6-db30-401a-b3fd-3b0ba3eaf643&sc_channel=ps&refid=d04c06f6-db30-401a-b3fd-3b0ba3eaf643

This is only for CLUSTER.
Other underlying resources will have separate charges.

AWS

EKS Cluster --> Elastic Kubernetes Service
Launch a EC2 Instance --> EKS Client VM
With this interact with the cluster.

Notes

Docker is used to create Container.
Docker Swarm is used to manage. Its a part of Docker.

Promotion - Canary Deployment

technonotes-hacker — Fri, 09 Oct 2026 03:45:31 +0000

a small, yellow songbird.
a small yellow bird that sings and is often kept as a pet.

What is Canary Deployment ?

Its a technique for rolling out new features or changes to a small traffic or instance before releasing the update to the entire system.
A small percentage of traffic is then routed to the new deployment , while the majority of the traffic continues to be served by the original deployment.
If the issues are detected during the canary deployment , it can be quickly rolled back to the original deployment.

Adavantage

Its a valuable tool for minimizing risk and ensuring high availability in complex distributed systems.

Target Deployment

Microservice

Process Flow

Plan and Create
Analyze
Roll Out

Implementation Plan

Deployment

Deployment team will take care via IR / CR accordyingly.

Canary Deployment will not be carried out for ?

DB changes
Low traffic Application
Request and Response changes
If the application as complex dependencies which one microservice will affect another in unexpected way then its difficult to isolate the issues.

How failures will be identified in canary deployment

POD wise logs will be maintained where the transaction failures can be verified.

Reference

Deploy a Release Using a Canary Deployment | Kubernetes

This tutorial walks you through deploying a canary release in Kubernetes. A canary deployment allows you to safely test a new application version with a small portion of production traffic before rolling it out completely. This approach helps minimize risk and enables rapid feedback from real users. For an overview of canary deployments, see Canary deployments in the Managing Workloads concept page. Objectives Deploy a stable version of an application Deploy a canary version alongside the stable version Route traffic to both versions using a Service Monitor the canary deployment Complete the rollout by scaling the canary and removing the stable version Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

kubernetes.io

Promotion - UNIX / Linux Basics - 2

technonotes-hacker — Thu, 08 Oct 2026 18:05:54 +0000

The kernel is the core foundation of the OS that directly interfaces with system hardware and controls process and memory operations.
Kernal --> its between the computer's hardware and its processes.
SIGTERM (signal 15) is the default termination signal sent by commands like kill, allowing the process to perform clean-up routines.
graceful and clean termination , allowing the application to save its active transactions before closing --> SIGTERM (signal 15).
/etc/shadow contains the secure encrypted password hashes and security aging constraints. --> sensitive system file securely stores encrypted user password hashes and account expiration details , only root user can access.
30 2 * * 1-5 /opt/bank/scripts/eod_report.sh. Exactly when does this script run? --> 30 specifies the minute , 2 specifies the hour (2:30 AM), and 1-5 specifies weekdays (Monday through Friday).

top utility displays a live, refreshing summary of system resource usage and active tasks sorted by resource consumption. --> dynamic, continuous real-time view of active system tasks, CPU utilization metrics, and memory consumption profiles on a Linux server.
sar is used for collecting, reporting, and saving historical system activity data over time.
vmstat reports virtual memory, paging, and block IO statistics, but does not offer an interactive real-time process manager interface.
netstat inspects network connections, routing tables, and interface statistics.
inode --> File names are mapped to inode numbers inside directory files; the inode itself holds the metadata and block pointers, omitting the filename string. It stores file attributes, permissions, and disk pointers, but does NOT store the actual file name.

/proc/meminfo is a virtual kernel file that provides live metrics regarding total, free, cached, and swap memory usage. --> virtual file system path exposes detailed real-time kernel memory statistics and swap utilization data.

Notes

what is hardened enterprise Linux environment ?

Promotion - UNIX / Linux Basics - 1

technonotes-hacker — Thu, 08 Oct 2026 17:50:21 +0000

kernel sysctl parameter should be tuned to increase the maximum number of queued incoming TCP connections awaiting acceptance

net.core.somaxconn --> maximum socket listen backlog queue size for incoming connections.
This is mainly for TCP connection backlog queue is overflowing

data-reconciliation batch utility is consuming excessive CPU cycles

what is data-reconciliation ? the systematic process of comparing, verifying, and fixing datasets from different sources to ensure they are accurate, consistent, and complete - தரவு சரிசெய்தல்.
A higher nice value means lower scheduling priority.
A lower nice value means higher scheduling priority

renice +n 19 -p [PID]
n stands for the "niceness"

If you are writing a script for BULK update accounts , you want the script to immediately abort if any single command in a pipeline fails.

set -euo pipefail
Correct! -e exits on error, -u exits on unset variables, and -o pipefail ensures pipeline failures propagate correctly.

no new transaction files can be written to the /data/txn partition , running df -h shows that the file system utilization is only at 48% capacity , bottleneck causing this failure?

Inode exhaustion on the partition
what is Inode exhaustion ? your file system has completely run out of available inodes (Index Nodes), even if you still have plenty of free gigabytes (GB) of actual disk space left.
Think of an inode as a metadata file in a library card catalog.
Every single file, directory, or link on a Linux partition requires exactly one inode to store its details (like file size, owner, permissions, and where the data blocks are physically located on the disk).
When a partition is formatted, a fixed number of inodes is allocated. This number usually cannot be changed without reformatting the drive.

df -i

unauthorized root access attempts on a critical RHEL-based core banking server

/var/log/secure
/var/log/auth.log

record authentication-related events, PAM notices, and sudo attempts.

finbatch is created to run automated night batch jobs , how to avoid this account from interactive terminal ?

/sbin/nologin
/bin/false

Setting these shell will gracefully rejects interactive login attempts while permitting system process execution.

end-of-day batch reporting script runs with user dbadmin , but consistently fails with command not found errors sqlplus: not found when triggered via cron , root cause of this execution discrepancy?

Cron initializes a minimal environment (often /usr/bin:/bin), omitting user-profile paths where specialized tools like Oracle sqlplus reside.
The cron daemon executes jobs with a minimal, restricted PATH environment variable.

end-of-day (EOD) interest calculation batch script is running , sudden high memory allocation, the Linux Out-of-Memory (OOM) killer targets , terminates a critical background database listener process instead of the non-essential batch job , to prevent , how can you configure the database listener process to be disfavored by the OOM killer?

Adjusting oom_score_adj to a strongly negative value (e.g., -1000) prevents the kernel from selecting that specific process during OOM events.

Write a negative value to /proc/[pid]/oom_score_adj for the listener process

Question

What is file descriptor constraint?

ulimit -n
ulimit -Hn
ulimit -n 4096
/etc/security/limits.conf

Notes

Nice and Renice Command in Linux --> https://www.geeksforgeeks.org/linux-unix/nice-and-renice-command-in-linux-with-examples/
What is file system utilization ?

Promotion - Miscellaneous

technonotes-hacker — Tue, 06 Oct 2026 18:08:58 +0000

What is DAST / SAST ?
Blue-Green deployment pipelines ?
Hardware Security Module (HSM) integration ?
mTLS ?

Promotion - NAS

technonotes-hacker — Tue, 06 Oct 2026 17:38:05 +0000

Network Attached Storage
file-dedicated storage device that is connected to a network.
Only authorized users allowed to store & retrieve data from centalized location via Ethernet.
Effortless storage upgrades.

Architecture

Components of NAS

Types of NAS Solution

Home or Personal NAS --> 1 TO 5 rive bays , used to store personal data, easy to setup , simple management interface , Low-cost storage solution , Used for media streaming, file sharing, and automatic backups.
Small Business NAS --> Supports 2–24 or more drive bays , multi-user access , Provides RAID configurations for data redundancy and protection , centralized file management , used for file sharing, backup, and small office applications.
Enterprise NAS --> high-speed data access for many users , large organizations that require high performance and scalable storage infrastructur , Used in data centers , advanced security, backup, and data management features .

Advantage

Disadvantage

Single Point of Failure
Limited Performance
Initial High Cost
Maintenance Complexity

Future Developments

AI Integration
Performance and Speed
Hybrid Cloud Integration
Sustainable Growth

Notes

NFS (Network File System) and CIFS (Common Internet File System).
NAS WORM --> Network Attached Storage ( Write Once Read Many )

Questions

Promotion - API - 1

technonotes-hacker — Sun, 04 Oct 2026 09:45:30 +0000

Why we need this interface ? To communicate between two different Language.
API means HTTP.
API is of REST & HTTP.
Fast API Tool --> its a framework in Python.
Its just a medium.
No validation takes place here.

Protocols

Set of rules or conditions.
Rules ? Based on the rules , the protocol will be defined.
We are going to communicate using HTTP Protocol only.
why we need follow ? If you follow , you will get the desired standard.

Methods

Hitting a GET request URL for testing purpose and you will get an output like below:

These outputs are maintained in the table structure.
If you are developing an API , if you can some standard via REST then it will be best in industry.
API as many categories like SOAP , REST , GRPC.
All these going to transfer only in HTTP Protocol.
Console Window --> Control + Shift + C
Cookie --> will have the details of the user.

Why not state-full ? It will be like residing in the same machine ,if you use stateless then it can go to any server , because the service may be hosted in many servers. It won't be in a single server.

State-full --> In the same machine.
State-less --> if the request goes to another server , this is useful.
There should be some COMMON format --> Data format --> On top of protocol only the data format will be sent. Eg., xml , json

https://www.tutorialspoint.com/xml/index.htm

Json format is equal to Dictionary in Python. ( nest dictionary & nested list )

Tools

bruno --> its a open source tool. ( Its a API client Tool )
Postman
How to install bruno ?

sudo apt update
sudo apt install bruno

Examples

Amazon --> ordered in first page and now its went to CART , if the cart doesn't know means , what will happen ? Here comes the HERO is STATELESSNESS ( making no relation between one API to another API is called STATELESSNESS ).

Notes

https://openweathermap.org/api --> we can invoke this API.

https://www.rfc-editor.org/info/rfc2616/ --> If you are transferring anything via HTTP , you should follow these rules, also you should use only these networks. All will be defined.

https://jsonplaceholder.typicode.com/ --> Testing purpose.
https://www.postman.com/

https://restfulapi.net/ --> You can find the tutorial.

Commands

env ( in linux )

Promotion - Database Replication

technonotes-hacker — Sat, 03 Oct 2026 04:03:28 +0000

This is the critical system design.
As it needs to provide redundancy , scalability and fault tolerance.
It tells the replication between primary database and its replicas.

Synchronous replication

data changes are replicated to one or more replicas in real time.
The transaction is not committed until one replica has acknowledged.
primary database and its replicas are always in sync, providing a high level of data consistency.
Example --> Banking application uses synchronous replication to ensure that all transactions are replicated to a secondary database in real-time for data consistency and disaster recovery purposes.

Working

Benefits

Strong Data Consistency --> Synchronous replication ensures that all replicas are up-to-date with the primary database.
Data Durability --> Since the transaction is not considered committed until it is replicated to at least one replica.

Challanges

Performance Impact --> as it must wait for acknowledgment from the replica(s) before completing transactions.
Network Latency --> as the primary database must wait for acknowledgment from the replica(s) over the network.

Asynchronous replication

data changes are replicated to one or more replicas after they are made on the primary database, without waiting for acknowledgment from the replicas.
faster transaction processing on the primary database.
slight delay in data consistency between the primary and replica(s).
Example --> An e-commerce website uses asynchronous replication to replicate product inventory data from the primary database to a secondary database for reporting and analysis purposes.

Working

Benefits

Improved performance on the primary database and reduced sensitivity to network latency. By not waiting for acknowledgment from the replicas before committing transactions.
Network Latency --> As it does not require immediate acknowledgment from the replicas

Challanges

Data Consistency --> Delay in data consistency between the primary database and its replicas, as the replicas are updated after the changes are made on the primary database.
Data Loss --> In case of a failure on the primary database before the changes are replicated to the replicas, there is a risk of data loss as the changes may not be replicated.

Semi-synchronous replication

method that combines aspects of synchronous and asynchronous replication.

data changes are replicated to at least one replica synchronously, ensuring strong data consistency for critical data, while other replicas are updated asynchronously for better performance.
balance between strong data consistency and improved performance.

Example --> When a customer initiates a funds transfer transaction, the transaction is processed on the primary database --> changes made by the transaction are replicated synchronously to at least one replica to ensure strong data consistency for critical financial data --> Other replicas are updated asynchronously to improve performance.

Working

Benefits

Strong Data Consistency --> strong data consistency for critical data by replicating changes synchronously to at least one replica.
Improved Performance --> other replicas asynchronously, semi-synchronous replication improves performance compared to synchronous replication.

Challanges

Increased complexity and resource usage compared to asynchronous replication, which must be carefully managed for optimal performance.
Synchronous updates can impact the performance of the primary database and increase resource usage compared to asynchronous replication. [ TBD ]

Differences

How to choose Replication Configuration ?

Data Consistency Requirements
Performance Requirement
Network Bandwidth and Latency
Failover and High Availability
Data Loss Tolerance

CONCLUSION

Database replication modes offer various trade-offs in terms of data consistency, performance, and complexity .

Notes

redundancy means duplicating critical components so a system does not fail if one part breaks.
fault tolerance --> system's ability to keep operating without interruption when one or more of its hardware or software components fail.
A trade-off is a situation where you give up one thing or quality in order to get or keep another, usually because you cannot have both at the same time

Promotion - Split-Brain Syndrome

technonotes-hacker — Sat, 03 Oct 2026 02:33:32 +0000

Critical failure state in HA & DR.
a single cluster fractures into isolated segments due to a network partition.
Why this happens ? --> Because the nodes can no longer communicate over their heartbeat network, multiple nodes simultaneously assume the primary/active role.
It leads to data corruption and catastrophic system behavior.

Eg., A scenario where both primary and secondary nodes mistakenly assume the role of the active primary server, leading to data corruption and conflicting transactions.

Root causes

Heartbeat Network Failures
Asymmetric Network Partitions
Application/OS Freezes (GC Pauses)

Prevention

To protect distributed systems, architects use a multi-layered prevention framework.

Notes

catastrophic --> Sudden failure.