Fibre Channel Storage Area Networks: components, topologies, ports, layers, addressing, and zoning.
A Storage Area Network (SAN) is a network whose primary purpose is transferring data between computer systems and storage devices. SAN implementations include Fibre Channel (FC) SAN, IP SAN (iSCSI/FCIP), and FCoE SAN.
شبكة التخزين SAN تربط السيرفرات بأجهزة التخزين عبر شبكة عالية السرعة (غالباً Fibre Channel) على مستوى الكتل. مكوناتها: HBA، كابلات، هَب، سويتش، ودايركتور.
A private high-speed highway built only for storage traffic.
SAN using Fibre Channel protocol; up to 16 Gb/s, lossless, highly scalable.
Enterprise block storage over FC fabric.
SAN using IP protocols (iSCSI, FCIP).
Block storage over Ethernet.
FC frames encapsulated over lossless Ethernet.
Converged LAN/SAN.
Host Bus Adapter — connects a server to the FC SAN.
An FC HBA card in a server.
Connects multiple devices in a switched fabric.
A 24-port FC switch.
A large, highly-available, modular FC switch for enterprises.
A core director with hundreds of ports.
Legacy shared-bandwidth device (FC-AL).
Used in older arbitrated loops.
FC supports point-to-point (direct), FC-AL (arbitrated loop, shared bandwidth, limited devices), and switched fabric (scalable, dedicated bandwidth — the dominant modern topology).
ثلاث طبولوجيات: نقطة لنقطة (اتصال مباشر)، حلقة محكّمة FC-AL (مشاركة)، ونسيج مُبدّل Switched Fabric (الأكثر استخداماً وقابلية للتوسع).
Point-to-point = a single private road; FC-AL = a shared ring road; Switched fabric = a city of interconnected highways.
| Topology | Bandwidth | Scalability | Note |
|---|---|---|---|
| Point-to-Point | Dedicated | 2 devices only | Direct link |
| FC-AL | Shared | Up to 126 devices | Loop, legacy |
| Switched Fabric | Dedicated | Very high | Modern standard |
FC port types define roles: N_Port (node port on server/storage), F_Port (fabric port on switch connecting a node), E_Port (expansion port linking two switches — ISL).
أنواع المنافذ في FC تحدد دور كل منفذ: N_Port على العقدة، F_Port على السويتش يقابل العقدة، وE_Port يربط بين سويتشين.
N_Port = your house door; F_Port = the street's connection point; E_Port = a bridge between two neighborhoods.
Node port on a host or storage device.
HBA port on a server.
Fabric port on a switch that connects to an N_Port.
Switch port facing a server.
Expansion port connecting two switches (ISL).
Inter-Switch Link between two FC switches.
Fibre Channel has 5 layers: FC-0 (physical/media), FC-1 (encoding), FC-2 (framing/flow control), FC-3 (common services), FC-4 (protocol mapping, e.g. SCSI over FC).
بروتوكول FC مكوّن من خمس طبقات من FC-0 (الفيزيائية) إلى FC-4 (الربط مع البروتوكولات العليا مثل SCSI).
Like the OSI stack but specialized for storage networking.
| Layer | Role |
|---|---|
| FC-4 | Protocol mapping (e.g. SCSI, IP over FC) |
| FC-3 | Common services |
| FC-2 | Framing, sequencing, flow control |
| FC-1 | Encoding / decoding |
| FC-0 | Physical layer (media, cables, speed) |
A World Wide Name is a globally unique 64-bit identifier (like a MAC address) for FC devices. WWNN identifies the whole node; WWPN identifies an individual port.
WWN عنوان فريد عالمي لأجهزة FC مثل عنوان MAC. WWNN يميّز العقدة كاملة، وWWPN يميّز كل منفذ.
WWNN = a person's national ID; WWPN = each of their phone numbers.
World Wide Node Name — identifies the entire device/node (adapter).
One WWNN per HBA card; dual-port HBA has one WWNN.
World Wide Port Name — identifies each port.
Dual-port HBA has two WWPNs.
Dynamic 24-bit address assigned during FLOGI: Domain ID + Area ID + Port ID.
239 domains × 256 areas × 256 ports ≈ 15.6M ports.
Unique number assigned to each switch in the fabric.
Up to 239 domain IDs available.
FC data is hierarchical: an Exchange contains one or more Sequences, and each Sequence contains one or more Frames (the smallest unit).
تنظيم البيانات في FC هرمي: Exchange يحتوي عدة Sequences، وكل Sequence يحتوي عدة Frames.
Exchange = a whole conversation; Sequence = a paragraph; Frame = a single sentence.
| Unit | Contains | Note |
|---|---|---|
| Exchange | Multiple sequences | Largest unit (a full operation) |
| Sequence | Multiple frames | Set of related frames |
| Frame | Payload | Smallest transmission unit |
FC login has three stages: FLOGI (Fabric Login — register with the fabric/switch, get an address), PLOGI (Port Login — establish a session with another N_Port), PRLI (Process Login — establish upper-layer protocol parameters, e.g. SCSI).
للانضمام إلى الـ Fabric يمر الجهاز بثلاث مراحل تسجيل دخول: FLOGI مع الـ Fabric، PLOGI مع الجهاز الآخر، وPRLI لتسجيل البروتوكول العلوي.
FLOGI = entering the building & getting a badge; PLOGI = introducing yourself to a colleague; PRLI = agreeing on what work you'll do together.
Fabric Login — node registers with the fabric and gets an FCID.
First step when a port comes online.
Port Login — session between two N_Ports.
Server logs in to a storage port.
Process Login — negotiates upper-layer (e.g. SCSI) parameters.
Establishes SCSI service parameters.
FC switches provide fabric services: Fabric Login Server (FFFFFE) for FLOGI, Name Server (FFFFFC) for WWN-to-FCID mapping, Fabric Controller (FFFFFD) for RSCN distribution, and Management Server (FFFFFA) for SAN management.
السويتش يوفر خدمات Fabric: Login Server للتسجيل، Name Server لتسجيل المنافذ، Fabric Controller لإرسال RSCN، وManagement Server للإدارة.
Like a building's reception (login), directory (name server), and announcement system (RSCN).
Predefined address FFFFFE; handles FLOGI.
Node sends FLOGI with WWNN/WWPN, gets FCID back.
Address FFFFFC; registers and maps WWNs to FC addresses.
Query all logged-in ports after FLOGI.
Address FFFFFD; sends RSCN on fabric changes.
Notifies nodes when zoning or topology changes.
Registered State Change Notification — alerts nodes of fabric changes.
Zoning limits which nodes receive RSCNs.
Beyond basic FC-SW: single-switch fabric (no ISLs), full/partial mesh (switches interconnected), core-edge (storage on core tier), and ISL link aggregation combining multiple ISLs into one logical port-channel for higher throughput.
بعد Switched Fabric، التصاميم تشمل: سويتش واحد، Mesh (كامل/جزئي)، Core-Edge، وتجميع ISLs في Port-Channel لزيادة النطاق.
Link aggregation = merging several highway lanes into one wider road.
Combines multiple ISLs into one logical ISL (port-channel).
3×8Gb ISLs → 24Gb port-channel.
| Topology | Description | Note |
|---|---|---|
| Single-switch | One switch, all nodes connected | No ISLs needed |
| Full mesh | Every switch connected to every other | Max 1 ISL hop |
| Partial mesh | Not all switches interconnected | Some paths longer |
| Core-edge | Edge + core tiers; storage on core | Scalable enterprise design |
BB_Credit (Buffer-to-Buffer Credit) is FC's flow control to prevent frame loss by tracking available receive buffers. Zoning segments the fabric for security/isolation: WWN zoning (by device name), port zoning (by switch port), or mixed.
BB_Credit آلية التحكم بالتدفق في FC لمنع فقدان الإطارات. أما Zoning فيقسم الـ Fabric لمجموعات معزولة للأمان، ويكون حسب WWN أو حسب المنفذ أو مختلطاً.
BB_Credit = traffic lights preventing congestion; Zoning = VIP areas that only certain guests can enter.
Buffer-to-buffer flow control counting available buffers.
Sender stops when credits reach zero.
Zones defined by device WWN (soft zoning).
Flexible: device keeps zone if moved to another port.
Zones defined by switch port (hard zoning).
More secure; tied to physical port.
Combines WWN and port-based zoning.
WWN tied to a specific port of another node.
Group of zones activated/deactivated as one entity; only one active at a time.
Production zone set vs test zone set.
| Aspect | WWN Zoning | Port Zoning |
|---|---|---|
| Based on | Device WWN | Switch port |
| Flexibility | High (move cables freely) | Lower (tied to port) |
| Security | Lower (WWN spoofing) | Higher |
| Also called | Soft zoning | Hard zoning |
The smallest FC transmission unit is a Frame. Each frame has five parts: SOF (Start of Frame), Frame Header, Payload (data), CRC (error checking), and EOF (End of Frame). Frames are grouped into Sequences, which form Exchanges.
أصغر وحدة نقل في FC هي الـ Frame. كل frame يتكون من 5 أجزاء: SOF (بداية)، Frame Header، Payload (البيانات)، CRC (للتحقق)، EOF (نهاية).
A frame is one envelope in a mail batch (sequence) that's part of a full shipment (exchange).
Start of Frame delimiter marking frame beginning.
First bytes of every FC frame.
Cyclic Redundancy Check for error detection.
Validates frame integrity on receive.
End of Frame delimiter marking frame end.
Last bytes signaling frame completion.