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A LUN (Logical Unit Number) is an identifier used in computer storage to distinguish between individual logical units, which are created from physical storage devices. Here’s a breakdown:

• Logical Unit: This refers to a virtualized portion of a physical storage device (like a hard drive or SSD) that has been assigned to a specific server or system.

• Number: The identifier used to refer to this specific logical unit within a storage system.

In Context:

LUNs are commonly used in SAN (Storage Area Network) environments. When a server connects to a SAN, it accesses storage through LUNs. Each LUN appears to the operating system as a regular hard drive, even though it might actually be part of a much larger shared storage pool.

Example:

A SAN might have a total of 10 TB of storage. An admin can carve out 1 TB chunks (LUNs) and assign them to different servers. Each server will only see its own LUN(s), not the whole 10 TB.

Would you like a visual diagram to help illustrate how LUNs work?

CIFS (Common Internet File System) and NFS (Network File System) are both protocols used for sharing files over a network, but they come from different backgrounds and are used in different contexts.

CIFS (Common Internet File System)

• Developed by: Microsoft

• Based on: An older protocol called SMB (Server Message Block)

• Platform: Primarily used in Windows environments

• Usage: Allows Windows computers to share files, printers, and serial ports over a network.

• Key features:

  • Supports user authentication and file permissions.

  • Works well in Active Directory environments.

  • Heavier in overhead compared to NFS (more "chatty").

Example Use Case: A Windows user mapping a shared network drive (like \\fileserver\sharedfolder) is using CIFS/SMB.

NFS (Network File System)

• Developed by: Sun Microsystems (now part of Oracle)

• Platform: Primarily used in Unix/Linux environments, but also supported on Windows.

• Usage: Allows Unix/Linux systems to share directories over a network.

• Key features:

  • More lightweight than CIFS.

  • Better performance for Unix/Linux systems.

  • Allows mounting of remote directories as if they were local.

Example Use Case: A Linux system mounting a directory from a remote server using a command like mount 192.168.1.10:/export/data /mnt/data.

CIFS vs NFS at a Glance

RAID stands for Redundant Array of Independent (or Inexpensive) Disks. It's a data storage virtualization technology that combines multiple physical drives into one logical unit to improve performance, fault tolerance, or both.

What RAID Does

RAID can:

• Improve performance (e.g., faster read/write speeds)

• Provide redundancy (protection against drive failure)

• Increase capacity (by pooling drives together)

Common RAID Levels

Real-World Example

Imagine you have 4 drives:

• RAID 0 will stripe data across all four for speed—but if one fails, all data is lost.

• RAID 1 will mirror data—each drive has a duplicate, so you're safe if one fails.

• RAID 5 will split data and parity across all drives—if one fails, data is still recoverable.

• RAID 10 will mirror and stripe—giving both speed and redundancy, but uses more drives.

Use Cases

• RAID 0: Video editing (high speed, low risk)

• RAID 1: Critical small business servers

• RAID 5: General-purpose storage with some protection

• RAID 10: High-performance databases or enterprise environments.

A SAN (Storage Area Network) is a high-speed, dedicated network that provides block-level access to storage for servers. It's used to connect servers to centralized storage devices (like disk arrays or tape libraries), making the storage appear locally attached to the operating system—even though it's actually located elsewhere on the network.

Key Features of a SAN

• High performance: Uses protocols like Fibre Channel, iSCSI, or NVMe over Fabrics for fast, low-latency communication.

• Block-level storage: Unlike file-level storage (like NFS or CIFS), SAN presents raw disk blocks to the OS, which formats and uses them as it sees fit.

• Centralized management: Storage resources can be pooled, allocated, and managed more efficiently.

• Scalability: You can add more storage or servers without major disruptions.

SAN Architecture Components

Why Use a SAN?

• High availability and redundancy: Great for critical applications like databases.

• Centralized backups and replication

• Shared access: Multiple servers can access the same storage pool.

• Enterprise-scale performance: Ideal for data centers.

SAN vs NAS (Quick Comparison)

The main difference between NAS (Network Attached Storage) and DAS (Direct Attached Storage) lies in how the storage is connected and accessed:

DAS (Direct Attached Storage)

• Connection: Directly attached to a single computer or server (e.g., via USB, SATA, SAS).

• Access: Only the host machine can access it (unless it shares files manually over a network).

• Examples:

  • External USB hard drives

  • Internal hard drive arrays (RAID) in a server

• Performance: Generally faster for single-host access since it doesn't go over a network.

• Use Case: Local backups, standalone servers, video editing systems.

NAS (Network Attached Storage)

• Connection: Connected to a network and accessed via protocols like NFS, SMB/CIFS, or FTP.

• Access: Multiple devices on the network can access shared files simultaneously.

• Examples:

  • Synology or QNAP boxes

  • File servers

• Performance: Depends on network speed (Gigabit, 10GbE, etc.), but optimized for file sharing.

• Use Case: Centralized file sharing, media servers, backups across multiple devices.

NAS vs DAS at a Glance

In simple terms:

• DAS is like a USB drive for one computer.

• NAS is like a shared folder for your whole network.

An IP (Internet Protocol) address is a unique numerical identifier assigned to each device connected to a network that uses the Internet Protocol to communicate. It's like a mailing address for your device, allowing it to send and receive data over the internet or local network.

Two Main Types of IP Addresses

1. IPv4 (Internet Protocol version 4)

   • Format: xxx.xxx.xxx.xxx (e.g., 192.168.1.1)

   • 32-bit address space (~4.3 billion addresses)

   • Still the most commonly used

2. IPv6 (Internet Protocol version 6)

   • Format: xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx

   • 128-bit address space (virtually unlimited)

   • Designed to overcome IPv4 limitations

Types of IP Addresses by Scope

Why IP Addresses Matter

• Let devices find and communicate with each other.

• Are used by routers, firewalls, and DNS servers to route data correctly.

• Allow services like web hosting, email, and streaming to function.

IP Example in Action

When you visit a website:

1. Your device sends a request to the site's IP address.

2. The site responds with the requested data (like a web page or video).

A VLAN (Virtual Local Area Network) is a way to logically segment a physical network into multiple separate networks — even if all devices are connected to the same physical switch.

What a VLAN Does

• Separates traffic: Devices on different VLANs can't talk to each other without a router or Layer 3 switch.

• Improves security: Limits broadcast domains and isolates sensitive traffic.

• Enhances performance: Reduces unnecessary traffic by confining broadcasts to each VLAN.

• Adds flexibility: Devices in the same VLAN can be spread across different physical locations.

How VLANs Work

Each device (or port) is assigned to a VLAN ID. Switches then tag or untag traffic using the IEEE 802.1Q standard to identify which VLAN the traffic belongs to.

Example Setup

Let’s say you have:

• VLAN 10: HR Department

• VLAN 20: Engineering

• VLAN 30: Guest Wi-Fi

Even if all these departments plug into the same physical switch, they act as if they’re on different networks. Traffic from VLAN 10 won’t reach VLAN 20 without explicit routing rules.

VLAN Benefits