Book-Notes Section 9 Flashcards
Difference Between Incremental and Differential Backup (Simple Explanation)
🔹 1️⃣ Incremental Backup (Fast, Small, Requires Full Chain to Restore)
✅ Saves only the changes since the last backup (whether full or incremental).
✅ Backups are smaller and faster, but restoring requires multiple steps.
📌 Example:
Monday – Full backup (Baseline).
Tuesday – Saves only changes since Monday.
Wednesday – Saves only changes since Tuesday.
Thursday – Saves only changes since Wednesday.
✅ Pros:
✔ Faster backups (only saves small changes).
✔ Uses less storage space.
❌ Cons:
❌ Restoration is slower (must restore the full backup + all incremental backups).
🔹 2️⃣ Differential Backup (Larger, But Faster to Restore)
✅ Saves all changes since the last full backup.
✅ Backups grow larger over time but restore faster.
📌 Example:
Monday – Full backup (Baseline).
Tuesday – Saves all changes since Monday.
Wednesday – Saves all changes since Monday.
Thursday – Saves all changes since Monday.
✅ Pros:
✔ Faster restoration (Only need the full backup + last differential backup).
❌ Cons:
❌ Takes more storage (each differential backup keeps growing).
🔹 Which One Should You Use?
✔ Use Incremental Backup if you need frequent backups and want to save storage space (but be ready for longer restore times).
✔ Use Differential Backup if you want a faster recovery process and have more storage space available.
What is Deduplication in the Context of Snapshots?
✅ Deduplication in snapshots is a process that removes duplicate data to save storage space.
✅ Instead of storing multiple full copies of a file or system state, only the unique changes between snapshots are saved.
🔹 How Deduplication Works in Snapshots
1️⃣ First Snapshot (Full Copy)
The system takes an initial full snapshot of data.
Example: A 100GB database snapshot is created.
2️⃣ Second Snapshot (With Deduplication)
A new snapshot is taken, but only the changed data is stored.
If only 5GB of data changed, the system does NOT store another full 100GB copy—it only saves the 5GB of changes.
3️⃣ Third Snapshot (More Deduplication)
If another snapshot is taken and only 2GB of new changes occur, only those 2GB are saved, not another full copy.
🔹 Main Difference Between Images and Snapshots (Simple Explanation)
🔹 Simple Explanation
✅ Image = A Full System Copy → Used to clone or deploy new machines.
✅ Snapshot = A Temporary Save Point → Used to restore a system to a previous state quickly.
📌 Example:
Image → Like a full backup of a phone that can be used to set up a new phone.
Snapshot → Like a “restore point” that lets you undo recent changes without wiping everything.
What is VDI (Virtual Desktop Infrastructure)?
✅ Virtual Desktop Infrastructure (VDI) is a technology that allows users to access a desktop operating system (like Windows) from a remote server instead of running it on their local computer.
✅ The entire desktop environment is virtualized and hosted in a data center, so users can access their desktop from any device, anywhere.
🔹 How VDI Works (Step-by-Step)
1️⃣ A user logs in to a VDI system from their device (laptop, tablet, thin client, or even a web browser).
2️⃣ The VDI server hosts virtual desktops in a data center or cloud.
3️⃣ The user’s desktop appears on their screen, but all applications, files, and processing happen on the VDI server, not the local device.
4️⃣ The user interacts with the virtual desktop just like a normal computer, but nothing is stored locally.
Are Thin Clients Dedicated to a VDI Server or Can They Log In and Out Anytime?
✅ Thin clients are NOT permanently tied to a specific VDI server—users can log in and log out whenever they like!
🔹 What Does Non-Persistent System Mean? (Simple Explanation)
✅ A non-persistent system is a system where any changes made during use are NOT saved after a reboot or logout.
✅ Every time the system restarts, it resets to its original state, erasing user modifications, installed apps, or temporary files.
🔹 How Non-Persistent Systems Work
1️⃣ A user logs into a non-persistent system (e.g., a virtual desktop).
2️⃣ They use applications, browse the internet, and make changes (e.g., saving files, installing software).
3️⃣ When they log out or reboot, the system resets to its default state.
4️⃣ The next user gets a fresh system, as if nothing had changed.
🔹 Why Use Non-Persistent Systems?
✔ Security → Prevents malware and unauthorized changes.
✔ Consistency → Every user gets the same clean system.
✔ Easier Management → IT doesn’t need to fix or update every system manually.
🔹 Where Are Non-Persistent Systems Used?
✔ Virtual Desktop Infrastructure (VDI) → Users get a fresh virtual desktop each time.
✔ Public Computers (Libraries, Schools, Cybercafés) → Ensures no user’s data is left behind.
✔ Call Centers & Shared Workstations → Employees get a standardized setup every login.
🔹 1️⃣ What is NAS (Network-Attached Storage)?
✅ NAS is a centralized storage system that connects to a regular network (LAN) and provides file-level storage to multiple users or devices.
✅ Think of it as a smart external hard drive that multiple people can access over Wi-Fi or Ethernet.
📌 How It Works:
A NAS device is plugged into a network (LAN).
Users access files like a shared folder, using protocols like SMB, NFS, or FTP.
The NAS has its own operating system, managing users, permissions, and file sharing.
✅ Example Use Cases:
✔ Home Users → Storing personal files, photos, and movies (e.g., Synology or QNAP NAS).
✔ Small Businesses → Central file sharing for employees.
✔ Backup Solutions → Storing backups from multiple devices.
🔹 2️⃣ What is SAN (Storage Area Network)?
✅ SAN is a high-speed network dedicated to connecting storage devices to servers, providing block-level storage.
✅ Unlike NAS, which works over a regular LAN, SAN operates on its own specialized network (usually using Fibre Channel or iSCSI).
📌 How It Works:
SAN storage devices are connected to a high-speed storage network.
Servers access storage as if it were a directly attached hard drive (block-level access).
This provides high performance and low latency, making it ideal for databases and virtual machines.
✅ Example Use Cases:
✔ Large Enterprises & Data Centers → High-speed storage for mission-critical applications.
✔ Virtualization Environments → Providing shared storage for VMs (e.g., VMware, Hyper-V).
✔ Databases & High-Performance Applications → Running large databases with low-latency storage needs.
When talking about Storage Area Networks (SANs), servers are not directly connected to storage devices. Instead, there is a separation where an intermediate networking infrastructure, such as a SAN switch or fabric, is used to manage and route data between servers and storage devices.
y using a switch (or fabric) to separate servers from storage devices, the storage devices exist on a different network—specifically, a Storage Area Network (SAN).
what does storage tiering for speed mean?
Storage tiering for speed means organizing data across different types of storage based on how fast the data needs to be accessed. Faster (and usually more expensive) storage is used for frequently accessed data, while slower (and cheaper) storage is used for rarely accessed data.
Simple Explanation:
How It Works in Storage Systems:
Hot Data (Frequently Used) → Fastest Storage
Stored on SSD (Solid State Drives) or NVMe for quick access.
Example: Active database transactions.
Warm Data (Occasionally Used) → Medium-Speed Storage
Stored on SATA SSDs or high-speed HDDs.
Example: Recent files or archived logs used occasionally.
Cold Data (Rarely Used) → Slowest Storage
Stored on tape drives or cloud archival storage.
Example: Old backups, compliance records.
Why Use Storage Tiering for Speed?
Cost Savings: Fast storage is expensive, so only critical data is stored there.
Performance Optimization: Ensures quick access to important data.
Efficient Data Management: Moves old or less-used data to lower-cost storage automatically.
Where is it Used?
Databases: Frequently queried data is on SSDs, while old records move to HDDs.
Cloud Storage: AWS S3 has Standard (fast), Glacier (slow) tiers.
Enterprise Systems: IT teams use tiering to optimize storage costs and performance.
what’s nonpersistence response control?
Nonpersistence response control is a security technique that ensures data or system changes do not last permanently after a session ends or after a task is completed. It helps maintain security and prevent unwanted changes from affecting the system.
Simple Explanation:
Imagine using a whiteboard to write notes, but when you leave the room, the board automatically erases everything so no one else can see or change your work.
Similarly, nonpersistence response control makes sure that once a system session ends or a task is finished, any changes made are removed or reset.
How It Works:
Temporary changes are allowed while a user is working.
When the session ends, the system automatically resets to its original state.
Any unauthorized or accidental modifications are erased.
Examples of Nonpersistence Response Control:
Virtual Machines (VMs) with Snapshots
A VM is used for testing, and once the session ends, it reverts back to its original state.
Read-Only Systems
Kiosk computers in public places automatically reset after each use to remove user data.
Temporary Files or Cached Data
Web browsers may store temporary session data, but it disappears when the browser is closed.
what’s code defined system used in cloud enviroments?
A code-defined system in cloud environments means that software (code) is used to set up, manage, and control IT resources like servers, networks, and storage, instead of doing it manually.
How It Works:
Write a script or configuration file that describes the system (servers, storage, networking, security rules, etc.).
Run the code, and the cloud platform automatically creates and configures the system.
The system can be repeated, changed, or deleted easily by modifying the code.
Examples of Code-Defined Systems in Cloud:
Infrastructure as Code (IaC)
Tools like Terraform, AWS CloudFormation, and Ansible allow users to define infrastructure using code.
Software-Defined Networking (SDN)
Networking is controlled by software rules instead of manually setting up routers and switches.
Software-Defined Storage (SDS)
Storage is managed and allocated through code, making it flexible and scalable.
Why Use Code-Defined Systems?
Faster Deployment: Automates system setup, reducing time and effort.
Scalability: Easily adds or removes resources as needed.
Consistency: Ensures every setup is the same, avoiding human errors.
Cost-Effective: Reduces manual work and optimizes resource use.
what does mounting a drive mean?
Mounting a drive means making a storage device (like a USB, external hard drive, or network drive) accessible to the operating system so you can read and write files on it.
Simple Explanation:
Imagine inserting a DVD into a player. The player recognizes it and allows you to watch the movie.
Similarly, when you mount a drive, the computer recognizes it and assigns it a location (like a drive letter in Windows or a folder in Linux/Mac).
How It Works:
You connect the storage device (USB, HDD, SSD, network storage).
The operating system detects it.
The drive gets mounted, meaning it is assigned a location (e.g., D:\ in Windows or /mnt/storage in Linux).
You can now access, read, and write files on the drive.
Unmounting a Drive:
Before removing the drive, it must be unmounted to ensure data is saved and prevent corruption.
what is content distribution network?
A Content Distribution Network (CDN) is a system of multiple servers spread across different locations that helps deliver websites, videos, and other online content faster and more reliably to users.
Simple Explanation:
Imagine a fast-food chain with restaurants in many cities. Instead of making customers travel to one main location, they can go to the nearest branch to get their food quickly.
A CDN works the same way—instead of making users download content from one central server, it stores copies of the content on multiple servers worldwide. Users get the content from the nearest or fastest server.
How It Works:
A website’s images, videos, and files are stored on CDN servers in different locations.
When a user visits the website, the closest CDN server delivers the content.
This reduces loading time and prevents the main server from getting overloaded.
what’s the difference between vertical and horizontal scaling ?
- Vertical Scaling (Scaling Up)
Upgrading a single machine to make it more powerful.
Think of getting a bigger and stronger engine for your car instead of buying another car.
How it works:
Adding more CPU, RAM, or storage to the same server.
Keeps the same number of machines, just making them stronger.
Example:
Upgrading a 4-core CPU to an 8-core CPU.
Increasing RAM from 16GB to 32GB in a database server.
Pros: ✔ Simple to implement.
✔ Works well for applications that can’t be split across multiple servers.
Cons: ❌ There’s a limit to how much you can upgrade.
❌ If the machine fails, everything stops.
- Horizontal Scaling (Scaling Out)
Adding more machines to share the workload.
Like hiring more workers instead of making one worker do everything.
How it works:
Instead of upgrading one server, you add multiple smaller servers.
A load balancer distributes traffic among them.
Example:
Adding 10 web servers instead of upgrading one big server.
Cloud services like AWS, Google Cloud, and Kubernetes use this method.
Pros: ✔ No limit to how many machines you can add.
✔ If one machine fails, others keep working.
Cons: ❌ More complex to manage.
❌ Some applications need to be designed to work across multiple servers.
what is a bastion or shell host?
A Bastion Host (also called a Jump Server or Shell Host) is a special security server used to provide controlled and secure access to other systems in a private network.
Simple Explanation:
Imagine a castle with high walls. Instead of letting everyone enter freely, there is a guarded gate (bastion host) that screens and controls who can go inside.
Similarly, a bastion host acts as a secure gateway that allows authorized users to access internal servers, while keeping attackers out.
How It Works:
Users first log into the bastion host using SSH (Secure Shell) or another authentication method.
Once inside, they can access internal servers in the private network.
The bastion host monitors and logs all activities for security.
Unauthorized users cannot directly connect to internal servers.
Industrial Camouflage in Site Security
Industrial camouflage in site security refers to disguising or concealing critical infrastructure, buildings, or assets to make them less noticeable or identifiable to potential threats, such as trespassers, vandals, or attackers.
Simple Explanation:
Imagine a military base painted to blend into the desert so it’s harder to see from the air.
Similarly, a data center, factory, or critical facility may be designed or disguised to look like a regular warehouse or office building to avoid attracting attention.
what’s the difference between piggybacking and tailgating attacks?
- Tailgating (No Knowledge or Approval)
The unauthorized person follows someone without their knowledge or permission.
Example: A stranger sneaks in behind an employee who opens a door with their key card.
This is often done by waiting for someone to open a door and slipping in unnoticed. - Piggybacking (With Knowledge or Approval)
The unauthorized person is allowed in by someone who knows them.
Example: An employee holds the door open for a friend, delivery person, or someone pretending to be from maintenance.
This often happens because of politeness or social engineering.
What is an Ultrasonic Sensor?
An ultrasonic sensor is a device that uses sound waves (beyond human hearing) to measure distance or detect objects.
Simple Explanation:
Think of a bat—it makes high-pitched sounds that bounce off objects, helping it “see” in the dark.
Ultrasonic sensors work the same way! They send out sound waves, wait for them to bounce back, and measure the time it takes to determine distance.
How It Works:
The sensor sends out ultrasonic sound waves (like an echo).
The waves hit an object and bounce back.
The sensor calculates the distance based on how long it took for the waves to return.
Where Are They Used?
✔ Car parking sensors → Help detect objects when reversing.
✔ Robotics → Robots use them to avoid obstacles.
✔ Security systems → Detect motion in restricted areas.
✔ Industrial automation → Measure liquid levels in tanks.
what’s the difference between simulation and failover tests?
✅ 1. Simulation Test
A simulation test is like a practice drill — you walk through what would happen during a real failure, but you don’t actually shut anything down.
🧾 Simple Explanation:
You pretend a disaster happens (like a server crash or power outage).
You talk through the steps: who does what, what systems are affected, and how to respond.
No real systems are touched.
✅ Used for:
Training teams
Testing response plans
Identifying gaps in the plan
🔍 Analogy:
Like a fire drill in a building — you don’t light a fire, but you practice what to do if it happens.
🔁 2. Failover Test
A failover test is a real test where you actually switch systems from the main environment to a backup or secondary system.
🧾 Simple Explanation:
You simulate a real failure by actually failing over to the backup system.
It checks whether the backup works properly and can take over the workload.
There’s real impact, so it’s often done during planned maintenance windows.
✅ Used for:
Verifying disaster recovery systems
Testing system performance under failover
Ensuring critical services keep running
🔍 Analogy:
Like actually cutting the power and switching to a backup generator to see if it works.
