How to Implement Storage Area Networks in ns2

To implement a Storage Area Network (SAN) in Network Simulator 2 (ns2) has encompasses to emulate a network that delivers the block-level storage access usually used in data centres to associate with servers to storage devices. A SAN permits the multiple servers to access storage devices over a high-speed network, usually using specialized protocols such as Fibre Channel, iSCSI, or FCoE (Fibre Channel over Ethernet).

Step-by-Step Implementation

Conceptual Overview

In a Storage Area Network:

  1. Storage Nodes: These nodes signify the storage devices like disk arrays or storage appliances.
  2. Server Nodes: These nodes denote the servers that access storage resources over the SAN.
  3. SAN Switches: These are specialized switches that links to storage and server nodes that make sure high-speed, low-latency data transfer.
  4. SAN Protocols: While ns2 doesn’t support directly for focused SAN protocols, we can mimic the network behaviour using a simple TCP/IP and high-speed links to approximate a SAN environment.

Step 1: Conceptualize the SAN Simulation

In this simulation, we will generate a scenario in which multiple server nodes access storage devices over an emulated SAN using high-speed links. The storage traffic will be transmitted via SAN switches that connect the servers to the storage nodes.

Step 2: Create the Tcl Script

The given below is an example Tcl script that emulates a simple Storage Area Network in ns2.

Example Tcl Script for Simulating a SAN in ns2

# Create a simulator object

set ns [new Simulator]

# Define the topography object (for a small data center area)

set topo [new Topography]

$topo load_flatgrid 1000 1000  # 1km x 1km area

# Create the General Operations Director (GOD) for the SAN simulation

create-god 8  # Number of nodes (4 servers + 2 storage devices + 2 SAN switches)

# Configure the nodes for the SAN using static routing

$ns node-config -llType LL \

-macType Mac/802_3 \

-ifqType Queue/DropTail/PriQueue \

-ifqLen 50 \

-antType Antenna/OmniAntenna \

-propType Propagation/FreeSpace \

-phyType Phy/WirelessPhy \

-channelType Channel/WirelessChannel \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace ON \

-movementTrace OFF

# Open trace and NAM files for recording the simulation

set tracefile [open san_out.tr w]

$ns trace-all $tracefile

set namfile [open san_out.nam w]

$ns namtrace-all-wireless $namfile 1000 1000

# Define a finish procedure to close files and end the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam san_out.nam &

exit 0

}

# Create SAN switches

set switch1 [$ns node]

set switch2 [$ns node]

# Create storage nodes (representing storage devices)

set storage1 [$ns node]

set storage2 [$ns node]

# Create server nodes (representing data center servers)

set server1 [$ns node]

set server2 [$ns node]

set server3 [$ns node]

set server4 [$ns node]

# Set initial positions for SAN switches, storage nodes, and server nodes

$switch1 set X_ 500.0

$switch1 set Y_ 300.0

$switch2 set X_ 500.0

$switch2 set Y_ 700.0

$storage1 set X_ 300.0

$storage1 set Y_ 300.0

$storage2 set X_ 300.0

$storage2 set Y_ 700.0

$server1 set X_ 700.0

$server1 set Y_ 200.0

$server2 set X_ 700.0

$server2 set Y_ 400.0

$server3 set X_ 700.0

$server3 set Y_ 600.0

$server4 set X_ 700.0

$server4 set Y_ 800.0

# Create high-speed links between SAN switches and storage nodes

$ns duplex-link $switch1 $storage1 1000Mb 5ms DropTail

$ns duplex-link $switch2 $storage2 1000Mb 5ms DropTail

# Create high-speed links between servers and SAN switches

$ns duplex-link $server1 $switch1 1000Mb 5ms DropTail

$ns duplex-link $server2 $switch1 1000Mb 5ms DropTail

$ns duplex-link $server3 $switch2 1000Mb 5ms DropTail

$ns duplex-link $server4 $switch2 1000Mb 5ms DropTail

# Define a custom procedure for simulating storage access traffic from servers to storage nodes

proc send_storage_data {src dst packetSize rate} {

global ns

# Create a TCP agent to simulate storage traffic

set tcp [new Agent/TCP]

$ns attach-agent $src $tcp

set sink [new Agent/TCPSink]

$ns attach-agent $dst $sink

$ns connect $tcp $sink

# Generate traffic using an FTP application

set ftp [new Application/FTP]

$ftp attach-agent $tcp

$ftp start

}

# Simulate storage access traffic from servers to storage devices

$ns at 1.0 “send_storage_data $server1 $storage1 1024 1000Mb”

$ns at 2.0 “send_storage_data $server2 $storage1 1024 1000Mb”

$ns at 3.0 “send_storage_data $server3 $storage2 1024 1000Mb”

$ns at 4.0 “send_storage_data $server4 $storage2 1024 1000Mb”

# Schedule the end of the simulation

$ns at 10.0 “finish”

# Run the simulation

$ns run

Step 3: Run the Tcl Script

Save the script with a .tcl extension, for instance, san_simulation.tcl. Then, execute the script using the following command in terminal:

ns san_simulation.tcl

Step 4: Visualize the Simulation

To visualize the simulation, open the configured NAM file using:

nam san_out.nam

Script Explanation

  • SAN Switches: The nodes switch1 and switch2 denotes SAN switches that connect the storage devices to the servers.
  • Storage Nodes: The nodes storage1 and storage2 denotes the storage devices, like disk arrays or storage appliances.
  • Server Nodes: The nodes server1 to server4 signify the data center servers that access the storage devices over the SAN.
  • High-Speed Links: The links among the SAN switches and the storage/server nodes are organized to be high-speed (1Gbps) to emulate the typical performance of a SAN.
  • Storage Traffic: The send_storage_data procedure mimic the data transfer from the servers to the storage devices using TCP that is a common protocol for reliable data transfer in SANs.

Customization

  • Different Protocols: While this simulation uses TCP over Ethernet links, that can adjust the script to approximate other SAN protocols such as iSCSI by modifying link speeds, packet sizes, or establishing latency.
  • Varying Link Capacities: Modify the bandwidth and latency of the links that mimic various network conditions, like changing load or congestion in the SAN.
  • Multiple Storage Devices: Attach more storage nodes and SAN switches to emulate a more complex SAN environment with multiple storage arrays and higher redundancy.
  • Storage Access Patterns: Test with numerous traffic patterns like read-heavy or write-heavy to mimic various kinds of workloads in the SAN.

Limitations

  • Simplified SAN Model: This script deliver a simple model of a SAN and does not account for the full complexity of real-world SAN environments like multipath I/O, advanced redundancy mechanisms, or storage virtualization.
  • No Physical Layer Simulation: The script does not emulate the physical layer features that particularly to SANs, like Fibre Channel or FCoE properties.
  • Limited Protocol Support: ns2 is not intended for SAN-specific protocols, so the simulation is limited to approximating SAN communication using TCP/IP.

In the above procedures will deliver the complete information about how the storage area network will execute and implement in the ns2 simulator. We deliver additional information about how the storage area network will perform.

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