Skip to main content

Hardware Redundancy

Hardware Redundancy
  • Use of additional hardware to compensate for failures
  • This can be done in two ways

    • Fault detection, correction and Masking. Multiple hardware units may be assigned to do the same task in parallel and their results compared. If one or more units are faulty, we can express this to show up as a disagreement in the results.

    • The second is to replace the malfunctioning units.

  • Redundancy is expensive, duplicating or triplicating the hardware is justified only in most critical applications
Two methods of hardware redundancy is given below are,
  • Static Pairing
  • N modular Redundancy (NMR)

Static Pairing

  • Hardwire processors in pairs and to discard the entire pair if one of the processors fails, this is very simple scheme

  • The Pairs runs identical software with identical inputs and should generate idientical outputs. If the output is not identical, then the pair is non functional, so the entire pair is discarded

  • This approach is depicted in the following figure, and it will work only when the interface is working fine and both the processors do not fail identically and around the same time.

[caption id="attachment_297" align="alignnone" width="500" caption="Static Pairing with Monitor"][/caption]

  • So the interface is monitored by means of a monitor which monitors the interface. If the interface fails, the monitor takes care and if the monitor fails, the interface takes care. If both interface and monitor fails, then the system is down. The monitor block is added as a dotted box in the above figure
N Modular Redundancy
  • It is a scheme for Forward Error Recovery.
  • It works with N processors instead of one and voting on their output and N is usually odd.
  • NMR can be illustrated by means of the following two ways

    • There are N voters and the entire cluster produces N outputs

    • There is just one voter

    [caption id="attachment_299" align="alignnone" width="607" caption="N Modular Redundancy"][/caption]

  • NMR clusters are designed to allow the purging of malfunctioning units. That is, when a failure is detected, the failed unit is checked to see whether or not the failure is transient. If it is not, it must be electrically isolated from the rest of the cluster and a replacement unit is switched on. The faster the unit is replaced, the more reliable the cluster.

    [caption id="attachment_298" align="alignnone" width="419" caption="Self Purging"][/caption]

  • Purging can be done either by hardware or by the operating system. Self purging consists of a monitor at each unit comparing its output against the voted output. If there is a difference, the monitor disconnects the unit from the system. The monitor can be described as a finite state machine with two states connect and isolate. There are two signals, diff which is set to 1 whenever the module output disagrees with the voter output and reconnect, which is a command from the system to reconnect the module.


Popular posts from this blog

Installation of NS2 (ns-2.35) in Ubuntu 20.04

Installation of NS2 (ns-2.35) in Ubuntu 20.04 LTS Step 1: Install the basic libraries like      $] sudo apt install build-essential autoconf automake libxmu-dev Step 2: install gcc-4.8 and g++-4.8 open the file using sudo mode $] sudo nano /etc/apt/sources.list Include the following line deb bionic main universe $] sudo apt update $] sudo apt install gcc-4.8 g++-4.8 Step 3:  Unzip the ns2 packages to home folder $] tar zxvf ns-allinone-2.35.tar.gz $] cd ns-allinone-2.35/ns-2.35 Modify the following make files. ~ns-2.35/ Change @CC@ to gcc-4.8 change @CXX@ to g++-4.8 ~nam-1.15/ ~xgraph-12.2/ ~otcl-1.14/ Change in all places  @CC@ to gcc-4.8 @CPP@ or @CXX@ to g++-4.8 open the file: ~ns-2.35/linkstate/ls.h Change at the Line no 137  void eraseAll() { erase(baseMap::begin(), baseMap::end()); } to This void eraseAll() { this->erase(baseMap::begin(), baseMap::end()); } All changes made Step 4: Open a new termi

Installing ns-3.34 in Ubuntu 20.04

This post shows how to install ns 3.34 in Ubuntu 20.04 LTS Prerequisites: Fresh installation of Ubuntu Version 20.04 LTS  ns3.34 can be downloaded from here Follow the video link for complete step by step instructions on the installation.  This version fixes the compilation issues of (bug in ns3.33)  Issue the following commands after opening a terminal  $ sudo apt update $ sudo apt install g++ python3 python3-dev python-dev pkg-config sqlite3 python3-setuptools git qt5-default gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar openmpi-bin openmpi-common openmpi-doc libopenmpi-dev tcpdump wireshark libxml2 libxml2-dev Unzip or untar the ns-allinone-3.34.tar.bz2 in the home folder (in my case its /home/pradeepkumar) $ cd ns-allinone-3.34/ $ ./ --enable-examples --enable-tests  Once the installation is completed, you may get an output show

Installation of ns3 in Windows 10 and Windows 11 OS using WSL (Windows Subsystem for Linux)

This post shows how to install ns-3.33 in Windows 10 through WSL (Windows Subsystem for Linux) This posts works for Windows 11 also (I have tested it on a Windows 11 ISO and it works the Same way as mentioned in the following post.) This post will work for ns-3.3x version. Prerequisites : Install Windows Subsystem for Linux with GUI: Please refer the following video  System Information: OS used: Windows 10 and WSL (Ubuntu 20.04) GUI: XServer for Windows NS3 Version: ns-3.33 See the following complete video on how to install ns3 in Windows 10 Step 0 : Open XLaunch Step 1 :  Open WSL using PowerShell and open it as Administrator Command:/  wsl $ xfce4-session The GUI of Ubuntu Opens within Windows 10 OS. Step 2 : Download ns3 from website through Mozilla Firefox browser Step 3: Open a Terminal  $ sudo apt update $ sudo apt install build-essential autoconf automake libxmu-dev python3-pygraphviz cvs mercurial bzr git cmake p7zip-full python3-matplotlib python-tk python3-dev qt5-q